revalidate

Revalidate refers to the act of validating something again to confirm its correctness, currency, or authenticity. In computing, revalidation commonly occurs after an initial validation to ensure data or resources remain accurate. The term appears in contexts such as caching, content delivery, authentication, and form or data validation.

In HTTP caching, revalidation enables a cache to verify a stored response with the origin server before reuse. The cache issues a conditional request using validators like ETag or Last-Modified. If the origin reports that the resource is unchanged, the server responds with 304 Not Modified and the cached copy is used; otherwise a fresh representation is returned and stored.

In Next.js, revalidate is used in Incremental Static Regeneration. It specifies a time interval, in seconds, after which a statically generated page is considered stale. On the next request after the interval, the server regenerates that page and serves the updated content, while still delivering the old cached page until regeneration completes.

Revalidation also occurs in authentication and session management, where a token or session may be re-validated against an issuer or database. This can involve refreshing tokens or rotating credentials to maintain security and access controls.

Benefits of revalidation include fresher data and reduced bandwidth compared to full rebuilds. Potential drawbacks include stale data if revalidation is too infrequent, or excessive validation overhead. Effective strategies balance data freshness, latency, and resource use.