The If-Range HTTP request header makes a range request conditional: if the condition is fulfilled, the range request is issued, and the server sends back a 206 Partial Content answer with the appropriate body. If the condition is not fulfilled, the full resource is sent back with a 200 OK status.
This header can be used either with the Last-Modified validator or with ETag, but not with both.
The most common use case is to resume a download, to guarantee that the stored resource has not been modified since the last fragment has been received.
| Header type | Request header |
|---|---|
| Forbidden header name | no |