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Understand byte-range requests, seeking, and why interrupted downloads may or may not resume.
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HTTP Range requests let a client ask for a portion of a resource instead of downloading it from the beginning. Browsers and media players can use ranges for seeking, while download clients may use them to resume data. Support depends on the server and how the resource is delivered.
A client can request a byte interval from a server, and a supporting server may respond with a partial-content status and the requested bytes. This mechanism operates at the HTTP resource level; it does not understand video scenes or timestamps by itself. Media players map a requested time to the bytes they need using container information and indexing.
When you jump forward in a video, the browser may request data near the new position rather than waiting for every earlier byte. Efficient seeking also depends on the container's metadata and server behavior. If a server ignores range requests, the player may need to download more data sequentially or may handle seeking less smoothly.
Resuming generally requires the client to know how many bytes are already stored and the server to accept a request for the remaining portion. A changed file, expired signed URL, missing session cookie, or server without range support can prevent continuation. Segmented streaming has a different structure: the client may need to fetch missing segments rather than continue one file.
Range behavior is visible through request and response headers, but a single observation does not establish that every download can resume. The response can depend on authentication, cache, proxy, and server configuration. If a permitted download stops, use the original browser workflow and its retry controls; do not attempt to evade authorization checks or DRM.
Only download content you own or have permission to save. Support depends on the website and media format; DRM-protected content is not supported.