An ETag is an HTTP response header providing a content-based validator that allows web clients and CDNs to make efficient conditional HTTP requests (304 Not Modified).
An ETag (Entity Tag) is an HTTP response header (RFC 7232 / RFC 9110) assigned by web servers and CDNs to represent the exact version of a requested resource. ETags enable lightweight conditional requests, allowing clients to revalidate cached content without transferring the full response body.
Inspect HTTP cache and ETag headers using the HTTP Headers Analyzer or compute cryptographic content hashes with the Hash Generator.
| Specification | Details |
|---|---|
| RFC Standard | RFC 9110 Section 8.8.3 |
| Strong ETags | Format: "33a64df551425fcc3e19f92734e8370f" (Byte-for-byte identical match) |
| Weak ETags | Format: W/"0815" (Semantically equivalent content, minor byte differences allowed) |
| Validation Headers | If-None-Match (for cache revalidation), If-Match (for optimistic concurrency control) |
| Response Code | HTTP 304 Not Modified when validator matches |
/api/users.HTTP 200 OK with ETag: "686897696a7c76fcb7" and response body.GET /api/users with If-None-Match: "686897696a7c76fcb7".HTTP 304 Not Modified and an empty body (~100 bytes), saving bandwidth and TTFT latency.Free, browser-based utilities to test, generate, and inspect HTTP Entity Tag (ETag) & Conditional Requests payloads directly.
Analyze HTTP response headers for security, caching, and compliance issues.
Generate and verify cryptographic hashes with multiple algorithms.
Build and test HTTP API requests with headers, body, auth, and response visualization.