Add to Calendar Button review

What it is

Add to Calendar Button is a JavaScript web component maintained by Calendarverse GmbH on GitHub (add2cal/add-to-calendar-button). You add it to a page, set the event details as attributes, and it shows a button with options for Google, Apple, Microsoft 365, Outlook.com, Teams, Yahoo and a generated .ics file. The npm package is add-to-calendar-button. On 2026-10-26 the latest version was 3.5.0 (released 2026-10-19), with 1,488 GitHub stars and 79,208 npm downloads in the week to 2026-10-22.

Pricing in plain words

The button is free to self-host and has no usage limits, because the links and .ics files are built in the visitor’s browser. Nothing is counted. Features that need a server are part of the separate paid Add to Calendar PRO service. The README lists them as hosted .ics files, RSVP with update emails to attendees, no-code customisation, an API and webhooks, and sharing to email and social channels. See the Add to Calendar PRO review for its prices.

Things to watch

• The licence is the Elastic License 2.0, which is not an OSI-approved open source licence. You can use and modify it, but you may not offer it to others as a hosted service or get around its licence-key checks. The maintainers say they no longer call it “open source” in marketing.
• It needs JavaScript, so it won’t run inside emails. For newsletters you need plain links or the PRO service.
• Without PRO, an event that changes after someone adds it won’t update in their calendar.
• The free version has no RSVP, analytics, API or webhooks.
• The README says it complies with GDPR, CCPA and LGPD by design because no event data is sent to a server. That is the maintainer’s claim; no DPA is offered for the free button.
• The package installs about 3.7 MB unpacked and depends on lit and the maintainers’ time zone library. Check the bundle size on your own page.