InvalidRequestContentException
AWS InvalidRequestContentException means the Lambda invoke request body cannot be parsed as JSON, or a request header value is invalid (HTTP 400).
Last reviewed: March 25, 2026|Editorial standard: source-backed technical guidance
What Does Invalid Request Content Exception Mean?
Lambda rejects the invoke payload at request parsing time, so function code never executes until body and header format are valid.
Common Causes
- -Invoke payload is not valid JSON for Lambda request parsing.
- -Content-type/header values do not match payload encoding.
- -A request header contains an invalid value (for example, malformed request ID format).
- -Gateway/proxy transformations corrupt request body structure.
How to Fix Invalid Request Content Exception
- 1Validate JSON payload and content-type before Invoke.
- 2Serialize payload using a single canonical JSON encoder.
- 3Retry with minimal valid event payload and inspect function logs.
Step-by-Step Diagnosis for Invalid Request Content Exception
- 1Capture raw request body and headers sent to Lambda Invoke API.
- 2Run strict JSON parsing/schema checks on outbound payload.
- 3Compare payload shape with handler expectations and contracts.
Payload Parse Integrity Checks
- -Inspect raw request bytes before transport to confirm strict JSON validity (example: trailing comma or control character breaks parser).
- -Audit UTF-8 encoding and escaping behavior across producers (example: double-escaped JSON string reaches Lambda as invalid JSON object).
Header and Gateway Transformation Checks
- -Verify
Content-Typeand transport headers remain consistent through proxies (example: gateway rewrites body while preserving stale content length). - -Compare SDK-direct invoke with gateway-routed invoke to isolate middleware mutation (example: direct call succeeds, API gateway path fails parsing).
How to Verify the Fix
- -Re-run Invoke and confirm payload is accepted without parse errors.
- -Validate function receives expected event schema in logs.
- -Confirm InvalidRequestContent errors stay cleared after rollout.
How to Prevent Recurrence
- -Validate invocation payload schema before send.
- -Use one canonical JSON serializer for event producers.
- -Add malformed/edge payload tests to CI.
Pro Tip
- -store canonical serialized event snapshots in pre-prod tests and replay them against invoke endpoints to catch parser-breaking serializer regressions early.
Decision Support
Compare Guide
HTTP 400 vs 422: Bad Request vs Unprocessable Content
Fix API payload issues faster by using 400 for malformed syntax and 422 for semantic validation failures, so clients correct format before business rules.
Playbook
CORS Error Fix Playbook (Preflight / Origin / Credentials)
Use this playbook to separate browser-enforced cross-origin policy failures from server-side CORS header and route defects and apply strict origin and credential controls safely.
Playbook
Validation Failure Playbook (400 / 422 / INVALID_ARGUMENT)
Use this playbook to separate malformed-request failures from semantic validation failures, then fix request contracts without broad server-side bypasses.
Official References
Provider Context
This guidance is specific to AWS services. Always validate implementation details against official provider documentation before deploying to production.