About rangelab

HTTP lets a client ask for part of a resource with a Range header; the server answers 206 Partial Content with a Content-Range describing the slice. The rules are small but edge-case-heavy — suffix ranges, clamping, multi-range multipart bodies, the 416 response — and an off-by-one quietly breaks downloads and players. Paste the header and the size and rangelab resolves it.

rangelab takes a Range request header and a resource size and applies the RFC 9110 rules: it parses each byte-range spec (integer, open-ended, or suffix), resolves the real byte intervals (with clamping and satisfiability), and reports the exact response — 206 single, 206 multipart/byteranges, 416, or an ignored-Range 200 — with the precise Content-Range, Content-Length, and Accept-Ranges headers. A second mode validates a Content-Range response value. Every figure follows a disclosed method, runs entirely in your browser, and makes no live request. It is informational; confirm against your real server.

It covers the tricky cases: bytes=-500 is the LAST 500 bytes; an end beyond the size is clamped; first ≥ size gives 416 with Content-Range: bytes */total; several ranges produce multipart/byteranges; a malformed Range is ignored for a plain 200.

Informational developer tool. Resolves the RFC 9110 rules statically — no live request; confirm against your real server.