NoSuchKey
AWS NoSuchKey (No Such Key) means the specified object key does not exist in the target bucket. In Amazon S3, this error returns HTTP 404.
Last reviewed: March 28, 2026|Editorial standard: source-backed technical guidance
What Does No Such Key Mean?
The bucket is reachable but object lookup failed, so clients receive 404 for that key and downstream renders, downloads, or batch jobs break until key resolution is fixed.
Common Causes
- -Object key path is incorrect, including prefix, delimiter, or file extension differences.
- -Key casing differs from uploaded object because S3 keys are case-sensitive.
- -URL encoding or decoding changes characters such as spaces, plus signs, or unicode in key names.
- -The object was moved, overwritten, or deleted but callers still use the previous key.
How to Fix No Such Key
- 1List objects under the expected prefix and copy the exact key returned by S3.
- 2Normalize key construction logic so upload and download paths produce identical keys.
- 3Verify URL encoding behavior for keys that include spaces or reserved characters.
- 4If object lifecycle rules removed the file, regenerate the object or update the reference key.
Step-by-Step Diagnosis for No Such Key
- 1Capture bucket, full key, and request ID from the failing operation.
- 2Run
ListObjectsV2for the prefix to confirm whether any near-match keys exist. - 3Review producer logs to confirm the exact key used at upload time.
- 4Inspect lifecycle/versioning events that might have expired or replaced the object.
Object Key Path Verification
- -Trace key construction end to end, including prefix, delimiter, and extension (example:
reports/2026/summary.jsonversusreports/2026/summary.JSON). - -Inspect URL-encoding normalization between producer and consumer (example: writer stores
%20, reader requests+for spaces).
Lifecycle and Version Checks
- -Audit lifecycle transitions and delete markers for the requested key (example: expiration rule created a delete marker for current version).
- -Verify read-after-write sequencing and replication timing (example: consumer fetches key before ingest pipeline commits object).
How to Verify the Fix
- -Repeat the failing GetObject/HeadObject call and confirm a successful response.
- -Validate downstream parsing and processing jobs consume the returned object correctly.
- -Confirm NoSuchKey error rates drop in application and CDN logs.
How to Prevent Recurrence
- -Use a shared key-builder library across all services that write/read the same objects.
- -Store canonical object keys in metadata instead of rebuilding them ad hoc.
- -Alert on unexpected object deletions and lifecycle-rule mismatches in critical prefixes.
Pro Tip
- -persist the authoritative key emitted at write time (event payload/metadata) and consume that exact key in downstream readers.
Decision Support
Compare Guide
403 Forbidden vs 404 Not Found: When to Hide Resources
Use 403 for explicit access denial, or 404 to conceal resource existence when security policy requires reducing endpoint and object enumeration risk.
Compare Guide
404 Not Found vs 410 Gone: Missing vs Permanent Removal
Learn when to return 404 (missing or temporary absence) versus 410 (intentional permanent removal), including redirect and cache implications.
Playbook
Resource State Playbook (404 / 410 / ResourceNotFound)
Use this playbook to separate temporary missing-resource lookups from permanent removals, then fix scope, lifecycle, and identifier drift safely.
Official References
Provider Context
This guidance is specific to AWS services. Always validate implementation details against official provider documentation before deploying to production.