I want to know how long Sentry keeps error events, and whether retention changes if I upgrade or downgrade my plan.

Sentry stores error events for:

Enterprise contracts can include custom error retention. Contact Sentry support if you need that option.

Retention is set when the event is ingested, based on the plan active at that time. If you upgrade or downgrade later, existing events keep the retention they received at ingest. New events use the new plan’s retention.

This article covers error events only. Other data types (such as spans, logs, replays, and attachments) have different retention periods. See the data retention periods documentation for the full table.

For related questions, see Is it possible to have a retention period shorter than 90 days? and How far back can errors and transactions be backdated when uploaded to Sentry?.