Range Request Builder

Analyze cache-related headers across layers. No input is sent to a server. Use it for first-pass revalidation and CDN mismatch troubleshooting.

Status

Runs in your browser. No input is sent to a server. Use this as a first-pass diagnostic step.

How to use

Enter a range and click “Build”. You can copy the Range header string.

Notes (this tool)

  • Range is in bytes. Check Accept-Ranges for support.

About this page

What does this tool do?

Generate Range headers to test partial content requests.

Useful for streaming, resume downloads, and chunked fetch testing.

Basics (Range syntax)

  • Range: bytes=start-end
  • Range: bytes=start-
  • Range: bytes=-suffix

Input examples

  • start-end: 0-1023
  • start-: 1024-
  • -suffix: -500

Common pitfalls

  • Sending Range when Accept-Ranges is none
  • Requesting an invalid range (416)
  • Range requests disabled by CDN/proxy

Debugging workflow (recommended)

  • Check support with Accept-Ranges Inspect
  • Build Range with this tool
  • Verify 206 and Content-Range in response
  • Accept-Ranges Inspect
  • Content-Length Inspect
  • Response Headers Parser

Recommendations (practical)

  • Use Range for large file delivery
  • Verify Accept-Ranges and 206/Content-Range
  • Use If-Range for safe resume

What this tool does

  • Build Range headers
  • Create start-end / start- / -suffix forms

Operational notes

  • Cache behavior changes across browser, CDN, and proxy layers, so compare captures from the same observation point.
  • Header-only diagnosis may be insufficient. Also review application cache invalidation strategy and key design.

Referenced specs

  • RFC 9110 (HTTP Semantics)
  • MDN: Range
  • MDN: Content-Range

FAQ

Can Range specify multiple ranges?

Yes, but single-range is usually the first step for testing.

What status code indicates Range success?

206 Partial Content.

References

  1. RFC 9110
  2. MDN: Range
  3. MDN: Content-Range

These links are generated from site_map rules in recommended diagnostic order.

  1. Content-Range Inspect — Parse Content-Range and inspect returned ranges
  2. Accept-Ranges Inspect — Parse Accept-Ranges and inspect partial-content support
  3. If-Range Inspect — Parse If-Range and inspect conditional range behavior
  4. Content-Length Inspect — Parse Content-Length and inspect size consistency

Range/Partial Content

Cross-check Range/Content-Range/If-Range to validate partial delivery