A word cloud with a “backend” in a single prompt: today Claude’s new artifacts save data without being published
In November 2025, a word cloud built with Claude stored everyone’s votes from a single prompt. Today the new artifacts save data without needing to be published.
On 9 November 2025, in Vibe Coding Educativo, an app built with Claude was being tested: a cloud of the countries from which members followed the group, which was meant to show everyone’s votes in real time. The group celebrated getting a “backend” from one prompt, and the questions came quickly: where was the data stored, and how could people be stopped from voting more than once? When asked, Claude itself spoke of an internal store, window.storage, with 5 MB per key.
Today Anthropic’s official help page on artifacts documents that storage. Whoever builds the app decides which data is personal, private to each user, and which is shared, visible to everyone; the first time someone uses the shared kind, Claude warns them. The limit is 20 MB per artifact, text only, on paid plans. What has changed is publishing: in artifacts created before 16 September 2026, storage only works once they are published, and unpublishing them deletes the data; new ones save without being published.
These apps can also call Claude: each user signs in with their own account and the usage is charged to their plan, not to that of whoever created the app.
A word cloud with a “backend” in a single prompt: today Claude’s new artifacts save data without being published
In November 2025, a word cloud built with Claude stored everyone’s votes from a single prompt. Today the new artifacts save data without needing to be published.
On 9 November 2025, in Vibe Coding Educativo, an app built with Claude was being tested: a cloud of the countries from which members followed the group, which was meant to show everyone’s votes in real time. The group celebrated getting a “backend” from one prompt, and the questions came quickly: where was the data stored, and how could people be stopped from voting more than once? When asked, Claude itself spoke of an internal store, window.storage, with 5 MB per key.
Today Anthropic’s official help page on artifacts documents that storage. Whoever builds the app decides which data is personal, private to each user, and which is shared, visible to everyone; the first time someone uses the shared kind, Claude warns them. The limit is 20 MB per artifact, text only, on paid plans. What has changed is publishing: in artifacts created before 16 September 2026, storage only works once they are published, and unpublishing them deletes the data; new ones save without being published.
These apps can also call Claude: each user signs in with their own account and the usage is charged to their plan, not to that of whoever created the app.
