Measure the UTF-8 wire size of an HTTP start line and header block before it reaches a proxy, CDN, or application server. The calculator reports total bytes, header count, the largest field, and a practical size warning. It accepts either raw header lines or a complete request or response head, while preserving repeated fields such as Set-Cookie.
HTTP Header Size Calculator converts the supplied text into a diagnostic result with concrete counts and structured export data. It keeps the original input in place so warnings can be traced back to the source.
A local diagnostic is useful for review, but it cannot replace the configuration limits and parsers used by the final server, proxy, browser, or Docker daemon.
Load the sample and run the tool. The output reports the parsed structure or findings derived from the exact sample shown in the input panel.
GET /reports?month=may HTTP/1.1 Host: example.com Accept: application/json X-Request-ID: 7f3a-9bc2
All core size processing runs in Vanilla JavaScript. Text is read locally, parsed once, and rendered into a read-only output area with optional JSON or CSV exports when structured rows are available.
This focused browser implementation does not perform network negotiation, authenticate credentials, build images, read a filesystem, or emulate vendor-specific size limits.
No. Its core processing runs in the browser and does not make a network request.
The page reports a focused error or warning and leaves the source text unchanged.
Yes, but review it first because local parsing cannot reproduce every server, Docker daemon, or registry decision.
Byte measurements use UTF-8, while parsers retain Unicode characters in readable output.
No. It is a diagnostic result; the receiving server or an actual Docker build remains authoritative.
| Field | Meaning |
|---|---|
| Summary | What was processed |
| Interpretation | Warnings and next checks |
| Stats | Tool-specific counts and timing |