Byte Range Request

Protocol

HTTP request using the Range header to fetch a specific byte slice of a resource. Essential for video seeking (jump to any timestamp), resumable downloads, and parallel chunk downloads. Returns 206 Partial Content.

Updated Mar 9, 2026

Full Explanation

A byte range request says: "I don't want the whole file, just bytes 1000–2000." The server responds with a 206 Partial Content and the requested slice. This is what makes video scrubbing work—when you click to minute 45 of a video, the player calculates the byte offset and requests just that segment.

For CDNs, range request support is critical. Video streaming (the majority of internet bandwidth) relies on it. If a CDN can't handle range requests properly, video players break, downloads can't resume after interruption, and PDF viewers can't load specific pages on demand.

There's a caching subtlety: the CDN should cache the full object and slice it per-request, not cache each byte range separately. Caching individual ranges wastes storage and creates a fragmented cache. Most CDNs handle this correctly, but it's worth verifying with your provider.

Examples

Requesting a specific byte range:

# Request bytes 0-999 (first 1KB)
curl -H "Range: bytes=0-999" -sI https://cdn.example.com/video.mp4
# HTTP/2 206
# Content-Range: bytes 0-999/52428800
# Content-Length: 1000

# Request last 1KB
curl -H "Range: bytes=-1000" -sI https://cdn.example.com/video.mp4

# Resume a failed download from byte 10485760
curl -C 10485760 -o video.mp4 https://cdn.example.com/video.mp4

Nginx enabling range requests for cached content:

# Enable slicing for large files (caches full object, serves ranges)
proxy_cache_path /cache levels=1:2 keys_zone=video:10m max_size=50g;

server {
    location /video/ {
        slice 1m;  # fetch from origin in 1MB slices
        proxy_cache video;
        proxy_cache_key $uri$slice_range;
        proxy_set_header Range $slice_range;
        proxy_cache_valid 200 206 24h;
    }
}

Frequently Asked Questions

HTTP request using the Range header to fetch a specific byte slice of a resource. Essential for video seeking (jump to any timestamp), resumable downloads, and parallel chunk downloads. Returns 206 Partial Content.

Requesting a specific byte range:

# Request bytes 0-999 (first 1KB)
curl -H "Range: bytes=0-999" -sI https://cdn.example.com/video.mp4
# HTTP/2 206
# Content-Range: bytes 0-999/52428800
# Content-Length: 1000

# Request last 1KB
curl -H "Range: bytes=-1000" -sI https://cdn.example.com/video.mp4

# Resume a failed download from byte 10485760
curl -C 10485760 -o video.mp4 https://cdn.example.com/video.mp4

Nginx enabling range requests for cached content:

# Enable slicing for large files (caches full object, serves ranges)
proxy_cache_path /cache levels=1:2 keys_zone=video:10m max_size=50g;

server {
    location /video/ {
        slice 1m;  # fetch from origin in 1MB slices
        proxy_cache video;
        proxy_cache_key $uri$slice_range;
        proxy_set_header Range $slice_range;
        proxy_cache_valid 200 206 24h;
    }
}

Related CDN concepts include:

  • Content-Encoding — An HTTP response header indicating the compression algorithm applied to the response body. Common values: …
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