Add to Calendar Market 2025 Analysis

EMAIL VS WEB

Apr 07, 2025

OUR TLDR - Sending Calendar Invites will replace add-to-calendar buttons in web and email channels for transactional and marketing use cases if appropriate.

Scheduling market vendors like Calendy educated millions of customers about sending actual permission-based calendar invites, tracking RSVPs, and using native updates, which was better than the Add to Calendar buttons.

We built the AWS Calendar Invite Server to adapt to these new message workflows.

Add to Calendar Marketing with Calendar Scheduling is at $6B Market Cap

The "Add to Calendar" feature has become an integral component of digital calendars and scheduling tools, allowing users to seamlessly incorporate events into their personal calendars. As of 2025, the market for calendar applications, which includes this feature, has experienced significant growth. Valued at approximately $5.71 billion in 2023, projections indicate it will reach around $16.37 billion by 2030, reflecting a compound annual growth rate (CAGR) of 10.4% during the forecast period .

In the mid-2010s, ECAL (a calendar marketing platform) was already serving millions of calendar activities per day, highlighting the substantial volume of calendar additions even early on. By 2020, Stanza (another major provider) reached20+ a million monthly unique users with its calendar tools. These figures suggest that annual add-to-calendar interactions likely number in the low billions worldwide when aggregating all platforms and methods. In terms of unique users, it’s plausible that tens of millions (potentially 100+ million)people globally add events to their personal calendars via these tools each year, given that Stanza alone had 13 million subscribers by 2020 and AddEvent serve 300,000+ corporate clients (each with their audiences).

Add to Calendar Email vs. Web Insertions

Email vs. Web Insertions: Add-to-calendar functionality is employed in email campaigns ( event invites, confirmations, newsletters) and on web pages or landing pages (event registration pages, product launch sites).

Usage is robust in both channels. In marketing emails, it’s extremely common – 87% of marketers use email for event promotion, often including calendar invite links to boost attendance. AddEvent’s data shows over 6 million unique events have been shared via email/newsletters using its service, underscoring heavy email usage. On the web, AddEvent’s widget is loaded about 20 a million times per day on websites– indicating that web/landing page insertions drive enormous interaction volume as well.

While an exact split is difficult, industry experts suggest a relatively balanced distribution: emails may account for roughly 40-50% of add-to-calendar link impressions, with web pages contributing 50-60%of volume (given the ubiquity of event landing pages and “Add to Calendar” buttons on sites).

In practice, these two channels often work together – for instance, a user might click an “Add to Calendar” button on a registration thank-you page or in a confirmation email alike. Both are essential: email insertions capture users at the moment of invite or confirmation, whereas insertionscatch users browsing event info online. In summary, the market’s size is best reflected by its widespread use: virtually every webinar, virtual event, concert ticket, sports schedule, or promotional event today leverages add-to-calendar links either in an email or on a webpage (and usually both), reaching a global audience in the hundreds of millions.

Both channels are critical. The convenience of a one-click calendar adds to a website caters to users at the point of signup or browsing, while email calendar links tap into the direct communication channel of attendees. Together, they make add-to-calendar technology ubiquitous in modern event promotions.

B2B - B2C Add-to-Calendar

B2B (Business-to-Business) Segment: In B2B contexts, add-to-calendar functionality has become a staple for driving event attendance, improving meeting show-up rates, and coordinating appointments. Companies regularly include calendar links in invites for webinars, virtual conferences, product demos, training sessions, and other client events. For example, marketers will embed “Add to Calendar” links in webinar invite emails or on event landing pages so that prospective attendees lock the date in their Outlook or Google Calendar immediately. This is vital for B2B lead nurturing – with so many webinars and virtual events, getting on a prospect’s calendar is half the battle in securing their attendance. According to event marketing stats, 75% of marketers say email is their most effective promotion channel, and these emails often leverage calendar links to convert interest into a calendar entry (since up to 45% of event ticket sales can come directly from email campaigns.

Corporate meeting scheduling tools (like Calendly or Chili Piper) also fall in this realm, automatically sending calendar invites for sales calls or consultations – ensuring that when a lead books a meeting, it’s instantly added to both parties’ calendars. In sum, B2B use of add-to-calendar is about reducing friction in scheduling and increasing attendance/participation in business events. Many B2B vendors integrate add-to-calendar with marketing automation (sending personalized ICS invites via Marketo, HubSpot, etc.) and even use it for internal purposes like booking client meetings or scheduling calls. The ROI is clear: getting on a client’s calendar means a committed time slot, which is why B2B marketers and sales teams heavily rely on this tech.

B2C (Business-to-Consumer) Segment: In B2C, add-to-calendar technology engages consumers and fans by integrating brand-related events into their personal schedules. This practice is often called “calendar marketing.” Brands increasingly use calendar invites to remind consumers about product launches, sales events, store openings, streaming events (like a live Q&A or a TV show premiere), and community events. For instance, an e-commerce retailer might offer an “Add to Calendar” button for the start of a holiday sale or a limited-time offer so that interested shoppers get a reminder on their phones.

Sports and entertainment is a vast B2C use case: sports leagues and teams provide calendar subscription links for schedules so fans can add the whole season or upcoming game dates to their calendars. This drives higher engagement – fans get automatic reminders for each game. A leading calendar platform in sports, Stanza, had over13 million subscribers to team schedules of 2020, illustrating how popular this has become for B2C sports fan engagement. Similarly, music festivals and concert promoters share add-to-calendar links for event dates and movie studios for release dates. Consumer-focused calendar marketing emphasizes being subtle and value-adding: experts note that calendars are personal space, so brands must only share genuinely helpful event info(the time a sale starts or a reminder of a TV episode) and not spam users with generic ads. When done right, it’s very effective – one study found consumers are 86% more likely to take action on something if there’s a related event on their calendar.

In everyday life, many consumers also encounter add-to-calendar when they receive things like flight itinerary emails, ticket confirmations, or restaurant reservations– these often include an ICS file or link to add the booking to a calendar.

In summary, B2C usage spans from marketing campaigns (to drive footfall or tune-in) to service transactions (to ensure the customer remembers their appointment or event), all aiming to integrate the brand into the consumer’s daily schedule in a helpful way.

Path to Multi Billion (2015–2025)

Over the past decade, add-to-calendar functionality has evolved from a fringe convenience to a must-have feature for events of all kinds. Here’s a brief historical overview of its development:

Early 2010s – Foundations: The underlying standard for calendar events, iCalendar (.ics) format, has existed since the late 1990s, but adoption picked up in the early 2010s as digital calendars (Google, Outlook, Apple) became mainstream. By 2012, entrepreneurs recognized the marketing potential of calendars. That year saw the founding of ECAL in Australia (2012) and Eventable in the U.S. (2012) – Both are aimed at leveraging personal calendars as a communication channel.
In these early days, implementation was clunky: sharing an event often meant emailing an ICS file attachment, which many recipients found confusing to download and import. Yet, even then, usage was growing – by 2014, ECAL was serving “more than 6 million calendar activities each day,” primarily through sports schedules. Also around 2013–2014, major platforms improved support: Google Calendar’s web links for event creation and Apple’s seamless handling of .ics attachments on iPhone made it easier for end-users to add events with one click.
Mid-2010s – Emergence of Add-to-Calendar Services: As demand grew, dedicated “Add to Calendar” services emerged to simplify the process for marketers and developers. AddThis (known for social share buttons) introduced an add-to-calendar widget around this time, and independent tools like AddToCalendar.com offered free embeddable buttons. Oracle bought the Addthis for a reported $200M shut it down in 2022.
In 2015, Stanza (formerly SpotOn) gained traction by partnering with sports teams; by that year’s end, Stanza’s add-to-calendar button had synced over 56 million sports events to fans’ calendars. This era also saw early adoption by business webinar platforms – event management software and email marketing services started to include “Add to Calendar” links in their templates. However, challenges remained: cross-platform compatibility was a headache (an ICS file might display differently in Google vs. Outlook, etc.), prompting innovators to seek a more uniform solution.
Late 2010s – Calendar Marketing Boom: Between 2016 and 2019, the concept of “calendar as a marketing channel” took off. Eventable and ECAL, in particular, evangelized calendar marketing. Eventable’’s platform enabled brands to create interactive calendar events with updated capabilities and analytics, attracting over 10,000 brands to use calendar channels by the late 2010s.
.Marketing use cases expanded beyond meetings: brands like Starbucks, DirecTV, and the NBA leveraged add-to-calendar for campaigns.

During this period, AddEvent (founded ~2017) emerged and quickly became popular for its simplicity – a one-stop service to generate add-to-calendar links and embed buttons. AddEvent’s growth was indicative of the market: by 2018–2019, it was used by thousands of companies and became the go-to solution integrated into platforms like MailChimp, Marketo, and others.
Technically, the late 2010s brought improvements: services offered multiple calendar options in one link(Google, Outlook, iCal, Yahoo, etc.), and subscription calendars (dynamic feeds users could subscribe to) were introduced.
For example, ECAL’s solution allowed real-time updates – if an event time changed, it would update on the subscriber’s calendar automatically. This was a response to user expectations for up-to-date info.
2020–2021 – Pandemic-Driven Utilization: The COVID-19 pandemic moved events online, massively boosting the use of add-to-calendar links. Virtual events and webinars proliferated, and every one had an add-to-calendar option in the invite. Calendars became even more central to people’s schedules (for managing virtual meetings, online classes, etc.). In 2020, ECAL reported 30–50% YoY growth for the past 3 years, and Stanza, by partnering with sports data providers, grew to 13+ million subscribers by 2020. This period also saw consolidation: in April 2023, Eventable (one of the early pioneers) ceased operations and directed its users to migrate to AddEvent. Essentially, AddEvent acquired or absorbed Eventable’s customer base, solidifying its position as the dominant standalone add-to-calendar service.
2022–2025 – Integration and Smart Features: Add-to-calendar tech has further integrated with other systems in recent years. Major email providers even built-in more innovative features – for instance, Gmail 2023 began rolling out an “Add to calendar” button automatically on certain emails (like those with dates) using AI to detect event info. Vendors like AddEvent expanded capabilities: offering RSVP tracking, analytics, and API integrations to embed calendar actions into CRMs and marketing clouds. The focus is on a seamless user experience: one click from any device, no downloads needed. The technology has matured to accommodate all significant calendars reliably (addressing the compatibility issues of earlier days). User awareness is also higher – in 2015,, a user might not have expected an “Add to Calendar” link, but by 2025, it’s assumed that any event registration will prompt you to immediately add it to your Google/Apple/Outlook calendar. Another recent development is the use of calendar adds as a re-engagement tool: for example, some brands now add an event to your calendar not just with date/time but also with a link or promo code in the description – effectively turning the calendar event into a marketing touchpoint.
This has been enabled by services like AddEvent and ECAL that allow rich text and updates in calendar entries. The past decade has thus seen the journey from simple ICS files to fully-fledged calendar marketing platforms that are interactive and analytics-driven.

Top Calendar Invite Vendors and Market Leaders

Over time, several vendors have become leaders in the add-to-calendar space, either as dedicated tools or as part of broader scheduling platforms. Below is a ranking of top vendors (circa 2024–2025) by estimated revenue, along with a brief on each:

1. Calendly – Estimated ~$270M annual revenue (2023)

Calendly is a scheduling automation platform rather than a pure add-to-calendar widget, but it heavily contributes to calendar adds. When someone schedules a meeting via Calendly, it sends calendar invitations that recipients add with one click. Calendly’s massive success (10 million+ users, $3B+ valuation) has made it a top “calendar integration” vendor by revenue. Its offering is a self-serve scheduling tool that integrates with Google, Outlook, etc., eliminating back-and-forth emails. Offering: Appointment scheduling links that create calendar events for all parties, integrations with Zoom and CRM, and team scheduling features.Use Cases: Predominantly B2B (sales, recruiting, client meetings) – e.g. a sales rep sends a Calendly link and once a slot is booked, an event is added to both people’s calendars.Note: While Calendly’s core business is scheduling, its impact on add-to-calendar usage is huge – effectively, it has trained millions to expect instant calendar invites for meetings.

2. Chili Piper – Estimated ~$40–43M annual revenue (2025)

Chili Piper is another scheduling and calendar automation tool focused on B2B revenue teams. It’s known for handling inbound meeting scheduling on websites (routing leads to the right rep’s calendar).Offering: It instantly schedules meetings or demos and drops them on the prospect and sales rep's calendars, integrating with Outlook/GCal. Chili Piper also offers event management for webinars (auto-sending calendar invites to registrants). Use Cases: B2B SaaS companies use it to increase the conversion of web leads by booking meetings in real-time. By volume of calendar invites, Chili Piper is a significant vendor (thousands of companies use it to send invites). It’s considered an alternative to Calendly in the context of “Add to Calendar” because it directly integrates calendar booking into workflows

3. AddEvent – Private; estimated revenue in the low millions. AddEvent is widely recognized as the #1 dedicated “Add to Calendar” service available.

It is a pure-play solution providing embeddable“Add to Calendar” buttons, ICS link generators, subscription calendars, and related tools for websites and emails. Offering: AddEvent’s platform allows event organizers to generate a single add-to-calendar link or button that works for all major calendar platforms (Google, Outlook, Apple, Yahoo, etc.). It also provides features like RSVP tracking, a centralized events calendar that users can subscribe to, and analytics on how many people added the event. Scale: It’s trusted by over300,000 companies globally, including large enterprises (their service is used by teams at Google, Microsoft, Amazon, etc. AddEvent handles extremely high volumes –20 million+ script requests per day from its embed buttons and 2.5 million+ calendar syncs per day for subscriptions.

While the company’s revenue is not public (likely a modest subscription-based model – Growjo estimates ~$200k, which may be low, by usage, it dominates the market. Use Cases: Widely used across industries (tech webinars, universities sharing academic calendars, e-commerce sale reminders, conference schedules, etc.). AddEvent has become the go-to for marketers who need a quick, reliable way to add “Add to Calendar” links in emails (it integrates with MailChimp, Marketo, Salesforce Marketing Cloud, and others out-of-the-box). Its ease of use and reliability across platforms have made it the “first choice” solution globally

4. Stanza – Private (venture-backed), niche focus. Stanza carved out a strong presence in the sports and entertainment segment. Founded in 2012, it pioneered the idea of fans subscribing to their favorite team’s schedule. Offering: An embeddable “Add to Calendar” button and calendar subscription service, primarily for sports teams, leagues, and media. Stanza’s platform not only adds events but keeps them updated if times change and can include rich content (scores, ticket links, etc.) in calendar entries. Scale: Over 13 million people subscribed to calendars via Stanza as of 2020

It also reported syncing 56 million+ events to users’ calendars by 2015 and working with 300+ professional teams (NFL, NBA, NHL, NCAA, etc.) Revenue is not disclosed; Stanza raised at least $4.3M in funding and likely earns through enterprise deals with sports organizations and possibly advertising or e-commerce tie-ins (it has explored ticketing and betting integrations Use Cases: Sports schedules, TV show calendars, community calendars. For example, a football team’s website might have a “Add to Calendar” for the season schedule – powered by Stanza. Fans get all games on their phone calendar, with automatic updates for scores or changes. Stanza’s success in B2C sports demonstrates the power of calendar marketing: it creates a direct communication channel to fans without needing email.

5. ECAL – Private (venture-backed), enterprise focus. ECAL (based in Melbourne) brands itself as a “calendar communications” or “sync-to-calendar” platform . It has a strong footprint in the sports, ticketing, and finance industries. Offering: ECAL provides customizable “Sync to Calendar” buttons that allow users to subscribe to an event schedule or series. Like Stanza, ECAL’s system can deliver real-time updates to those calendar entries and even supports transactions (they partnered to enable in-calendar ticket purchases, etc.) Scale: ECAL had over 100 major clients by 2014 (NFL teams, media, etc.) and was delivering millions of events daily. It reported that70% of adults rely on a digital calendar to manage their life – a statistic from its 2018 user survey underscoring the market need it fills. While smaller than AddEvent in self-service adoption, ECAL’s enterprise deals (e.g., with the English Premier League, NCAA, etc.) mean it likely generates several million dollars in revenue via SaaS contracts. In 2020, ECAL secured additional funding and grew 30–50% YoY, indicating healthy finances .Use Cases: Similar to Stanza, sports fixtures, broadcast schedules, ticket on-sale date reminders, and billing/payment reminders (some financial institutions use ECAL to remind customers of due dates via calendar entries). ECAL’s value prop is high engagement – by its claims, calendar reminders achieve 5–20× higher awareness than email and 2× higher purchase rates for promotions. This has positioned ECAL as a top vendor for organizations looking to boost engagement through calendars rather than email.

Other Notable Mentions: A few other players deserve note besides the above. Microsoft Outlook and Google (Workspace) Calendar are not vendors of “add-to-calendar software,” However, since they are the primary endpoints, their influence is significant. Microsoft and Google have also added features (like Outlook’s one-click “Add to Calendar” for .ics in email and Gmail’s smart add-to-calendar) that somewhat compete with third-party tools by making the process more native. Apple Calendar (iCloud) is similarly just a platform, but Apple’s intuitive integration (tapping a .ics on iPhone automatically adds it) has helped drive the adoption of calendar invites in consumer scenarios. Some new startups and open-source solutions have emerged, too: for example, Calndr. link and CalGet are free to link generators as alternatives to AddEvent – useful for individuals or small projects (though not significant revenue-wise). Event management platforms like Eventbrite, Cvent, and Zoom also have built-in add-to-calendar features (usually sending .ics files or links in their confirmation emails). While not standalone vendors, they contribute to the market usage. Overall, the vendor landscape has a clear leader in AddEvent for dedicated tools and significant adjacent players in scheduling (Calendly, etc.) and specialized calendar marketing (Stanza, ECAL). The consolidation (e.g., Eventable’s users moving to AddEvent ECAL acquiring smaller rivals like Rokt Calendar suggests a maturing market with a few dominant solutions.

User Adoption and Platform Support

Add-to-calendar features enjoy broad adoption by users across all major calendar platforms. Digital calendars have become an essential daily tool for a majority of people – a 2018 survey found that 70% of adults rely on a digital calendar to manage their schedule. This high reliance sets the stage for why add-to-calendar is so effective: if an event is on someone’s calendar, they are far more likely to remember and attend it.

Annual User Interaction Estimates: Considering the combined user base of calendar platforms, the number of users interacting with add-to-calendar features each year is enormous. Google Calendar alone has about 500 million monthly active users, and Microsoft Outlook (consumer & 365) has on the order of 400–450 million active users. Apple’s Calendar (the default on hundreds of millions of iOS and macOS devices) and Yahoo Calendar (used by legacy Yahoo Mail users) add tens of millions. Not every user will click an “add to calendar” link in a given year. Still, a substantial fraction will – especially as remote work and virtual events have habituated more people to use digital calendars. By piecing together available data: Stanza’s 13 million subscribers, Eventable’s 10,000+ brand clients (each with possibly thousands of users), AddEvent’s 300k corporate users driving millions of adds, etc., it’s reasonable to estimate over 100 million individual end-users take advantage of add-to-calendar features annually. Many are repeat users (e.g., a power user might add dozens of events annually).

In total volume, as mentioned earlier, the interactions likely run into the billions of calendar adds per year globally. For example, if AddEvent alone handles millions of event adds/year and Stanza delivered 56 million events by 2015 (and far more since), aggregating all methods (emails with .ics files, website buttons, calendar subscription feeds) readily crosses the 1 billion mark over a year worldwide. This figure includes everything from a person clicking “Save to calendar” for a Zoom meeting to someone auto-adding all Formula 1 race dates via a subscription service.

Major Calendar Platform Support: A key to the proliferation of technology is that it supports all major calendar platforms in a user-friendly way. Each platform has its format or method, and the add-to-calendar ecosystem has unified them:

Google Calendar: Supports direct web links (a URL that pre-populates event details on the Google Calendar web app). All leading add-to-calendar services generate a Google link for one-click adding. Given Google’s ~500M user base, this is crucial. Many tech-savvy users (especially B2B) prefer this. Google Calendar’s dominance on Android phones and in Workspace means any event targeting a broad audience must accommodate it.
Apple Calendar (iCal): Apple’s Calendar (iPhone, iPad, Mac) uses the ICS file format. Add-to-calendar buttons, therefore, often offer a .ics file download, which Apple devices handle gracefully – tapping it on iOS adds to the Calendar app. Apple users represent a large portion of mobile calendar users (in one survey, ~47% used a mobile calendar vs 23% on desktop, implying a lot of iPhone/Android usage. Thus, services ensure compatibility with Apple’s system (often labeling it “Apple Calendar” or “iCal” in options).
Microsoft Outlook (and Office 365): This includes the desktop Outlook application (often used with corporate Exchange servers) and the Outlook.com web calendar for consumers. Outlook can directly open ICS files as calendar entries, so the standard approach is providing an ICS file download for Outlook users. Some tools also give a tailored link or integration for Office 365. With Microsoft boasting hundreds of millions of Office users, the support here is non-negotiable. Notably, many enterprise users expect meeting invites (in .ics format) – “Add to Calendar” links in webinar invites often specifically say “for Outlook”. Modern services like AddEvent generate multiple versions of ICS behind the scenes to account for Outlook’s quirks (to ensure time zones, etc., display correctly.
Yahoo Calendar: Though less prominent today, Yahoo was once a big player. Yahoo Calendar can accept events via a web link (similar to Google’s method) or via ICS. Add-to-calendar services typically include a Yahoo option. A subset of users (Yahoo Mail’s user base, which is still significant) might use this.
Other Platforms: This category includes calendars like Microsoft Teams/Exchange (generally covered by Outlook/Office 365 ICS), IBM Notes, and various mobile apps. Most of these can ingest ICS files. The universality of the ICS standard is why virtually all add-to-calendar solutions provide an ICS file download as a fallback – it will work on any calendar application that a user might have. New calendaring apps (like Proton Calendar or Fastmail’s calendar) also support ICS imports and sometimes Google-format links. The goal is to leave no user unable to add the event, regardless of their chosen calendar app.

Add to Calendar User Experience and Trends

Today’s users are familiar with the add-to-calendar process. It’s now common that after you RSVP or register for something, you’re immediately prompted to “Add this event to your calendar.”

This expectation has driven adoption sky-high. The ease of one-click adds (versus the old multi-step import of the past) is a big reason – modern implementations mean a user on a smartphone can tap one link and have the event appear in their calendar app within seconds. Surveys indicate people check their digital calendars 12 times per day on average, so once an event is on the calendar, the likelihood of awareness is very high. Marketing studies show an 86% increase in engagement when users have a calendar event set(versus just receiving an email reminder). Click-through rates from links inside calendar event descriptions can be extremely high – Eventable noted calendar event links got 100× higher click-through than typical digital ads . These figures underscore why the user adoption has grown: consumers and professionals alike find calendar reminders more helpful and less intrusive than other channels, so they willingly interact with them.

In summary, all major calendar platforms are well-supported and heavily used in the add-to-calendar ecosystem. User interaction with this technology is now a routine part of digital life. The convergence of high digital calendar usage (billions of events managed daily) and the convenience of one-click additions has solidified 'Add to Calendar' as a globally adopted feature. It bridges the gap between an invitation and attendance by leveraging the ubiquitous personal calendar – truly integrating events into users’ daily routines, whether in a business setting or personal life. The result is a thriving global market for these tools, and a world in which forgetting an event is far less likely than a decade ago, thanks to that simple “Add to Calendar” button.

TLDR CONCLUSION

Sending Calendar Invites will replace add-to-calendar buttons in web and email channels for transactional and marketing use cases if appropriate.