416 - Range Not Satisfiable

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What Does Range Not Satisfiable Mean?

Partial content retrieval failed because requested byte ranges do not map to the current representation, so resumable reads break until offsets are corrected.

Common Causes

• -Resume download requests bytes range beyond current object length after object was replaced with smaller file.
• -Cached Content-Length metadata is stale at CDN edge, so client computes invalid byte window against origin.
• -Video player generates suffix range larger than small asset size, and origin returns range not satisfiable.

How to Fix Range Not Satisfiable

1. 1Fetch current object length (for example via HEAD) and rebuild Range header within valid bounds.
2. 2Reset stale resume offsets when resource size/version changed since previous download attempt.
3. 3Use single-range requests first to isolate range-calculation defects before multi-range optimization.

Step-by-Step Diagnosis for Range Not Satisfiable

1. 1Capture the exact Range header sent and the response metadata returned with 416.
2. 2Verify current representation length and compare it against requested byte intervals.
3. 3Check for stale resume metadata after upstream resource replacement or truncation.
4. 4Retest with a known-valid range (bytes=0-1023) and then expand range logic incrementally.

curl -i -X GET https://api.example.com/v1/resource -H "Range: bytes=9999999-10000000"
# Response:
# HTTP/1.1 416 Range Not Satisfiable
# {"error":"Range Not Satisfiable","code":"416"}

const response = await fetch('https://api.example.com/v1/resource', {
  method: 'GET',
  headers: { 'Accept': 'application/json', 'Range': 'bytes=9999999-10000000' }
});
if (response.status === 416) {
  console.error('Handle 416 Range Not Satisfiable');
}

import requests

response = requests.get(
    'https://api.example.com/v1/resource',
    headers={'Accept': 'application/json', 'Range': 'bytes=9999999-10000000'}
)
if response.status_code == 416:
    print('Handle 416 Range Not Satisfiable')

Seen in Production

Debugging Tools

• -curl -v with explicit Range headers
• -HEAD response inspection for Content-Length and ETag
• -Download-resume client logs
• -CDN/origin metadata comparison dashboards

How to Verify the Fix

• -Repeat resumable reads and confirm valid ranges return expected partial content paths.
• -Run boundary tests for first byte, last byte, and end-of-file resume offsets.
• -Confirm clients recover gracefully by resetting offsets when server signals invalid range.

How to Prevent Recurrence

• -Store and validate resource length/version metadata before issuing resumed range requests.
• -Add integration tests for resume logic across file replacement and truncation scenarios.
• -Standardize range-header builders to avoid manual offset arithmetic in clients.

Pro Tip

Related Errors

Official References

• -RFC 9110 Section 15.5.17 - 416 Range Not Satisfiable definition
• -IANA HTTP Status Code Registry - 416 Range Not Satisfiable
• -MDN Web Docs — 416 Range Not Satisfiable
• -HTTP Official Documentation