Error codes

The Filebase S3 API returns the same error format as AWS S3 — XML body, standard HTTP status code, and the standard set of error codes.

Error response format

<?xml version="1.0" encoding="UTF-8"?>
<Error>
  <Code>NoSuchBucket</Code>
  <Message>The specified bucket does not exist.</Message>
  <Resource>/missing-bucket</Resource>
  <RequestId>d40f7c5a-...</RequestId>
</Error>

Every modern S3 SDK parses this format and surfaces the Code, Message, and RequestId as exception fields. When opening a support ticket, including the RequestId lets Filebase correlate the request to backend logs.

Common errors

HTTP	Code	Cause
400	InvalidArgument	A request parameter is malformed.
400	InvalidBucketName	Bucket name doesn't follow naming rules.
400	MalformedXML	XML body couldn't be parsed (CORS or lifecycle config).
400	EntityTooLarge	Object exceeds the 5 GB single-PUT limit — use multipart upload.
403	AccessDenied	Credentials lack permission, or the bucket ACL forbids the operation.
403	SignatureDoesNotMatch	Signing key or signed string doesn't match what Filebase computed — usually a region or endpoint mismatch.
403	RequestTimeTooSkewed	Client clock differs from server time by > 15 minutes.
403	SignatureExpired	Pre-signed URL has expired.
404	NoSuchBucket	Bucket doesn't exist on this account.
404	NoSuchKey	Object doesn't exist.
404	NoSuchUpload	Multipart upload ID is invalid or has been aborted.
409	BucketAlreadyExists	Bucket name is already taken globally.
409	BucketAlreadyOwnedByYou	You already created this bucket.
409	BucketNotEmpty	Trying to delete a bucket that still contains objects.
411	MissingContentLength	Body present but Content-Length header missing.
412	PreconditionFailed	An If-Match / If-None-Match precondition failed.
416	InvalidRange	The Range header asks for bytes outside the object.
501	NotImplemented	Operation isn't supported on Filebase — see the compatibility matrix.
503	SlowDown	Rate limit exceeded — back off and retry.

Retry behavior

Most SDKs retry idempotent operations (GET, HEAD, LIST, DELETE) automatically with exponential backoff on 5xx errors and 503 SlowDown. For non-idempotent operations (PUT, POST, multipart Complete) the SDK is more cautious — verify before retrying.

The default backoff in the AWS SDKs is exponential with jitter, capped at a few seconds. This works well against Filebase without any tuning.

Diagnosing SignatureDoesNotMatch

This error is almost always one of:

• Wrong region. Use auto (or us-east-1 if your tool refuses auto).
• Wrong endpoint. Use https://s3.filebase.io for the new S3 tier.
• Wrong signature version. Filebase requires SigV4; SigV2 is rejected.
• Body modified between signing and sending. Check that no proxy or middleware (compression, charset conversion) is altering the request body.

What's next

• Compatibility matrix
• Authentication
• Rate limits