BadRequest
ARM returns `BadRequest` when deployment values or request structure do not match what Resource Manager expects.
Last reviewed: February 17, 2026|Editorial standard: source-backed technical guidance
What Does Bad Request Mean?
Request validation failed before execution, so no resource changes occur until malformed fields and contract mismatches are corrected.
Common Causes
- -Payload includes invalid property values or types for the selected resource API version.
- -Required deployment parameters are missing, null, or mismapped at runtime.
- -Request body formatting or serialization produces invalid ARM JSON structure.
- -Template exported from existing resources contains unsupported or stale fields.
How to Fix Bad Request
- 1Read inner status/error details and identify the exact offending property or parameter.
- 2Compare payload against current template reference for resource type and API version.
- 3Correct malformed fields and rerun ARM validation before full deployment.
- 4Retest with minimal valid payload, then add optional sections incrementally.
Step-by-Step Diagnosis for Bad Request
- 1Capture full request payload and response inner errors from deployment operation logs.
- 2Validate rendered template/parameter files used by the runtime, not just source templates.
- 3Cross-check value ranges, enums, and required blocks against provider schema docs.
- 4Run incremental replay to isolate the first field combination that triggers
BadRequest.
Inner Error Chain and Payload Parsing
- -Parse nested
detailsandinnererrorfields to find root property failure (example: top-level BadRequest hides nested invalid network security rule value). - -Diff source template and rendered runtime payload (example: CI token replacement injects string into numeric field).
Schema Drift and API Version Checks
- -Validate API-version-specific fields before deployment (example: property removed in newer provider API remains in legacy template).
- -Inspect exported templates for non-deployable read-only fields (example: export includes runtime-only status block that ARM rejects on create).
How to Verify the Fix
- -Run validation and confirm
BadRequestno longer appears for the same request path. - -Execute deployment and verify resources provision without request-structure failures.
- -Ensure follow-up operations in the same template also pass with corrected payload.
How to Prevent Recurrence
- -Introduce contract validation gates on rendered deployment payload artifacts.
- -Track API version upgrades with schema-diff review before production rollout.
- -Reject deployment bundles containing unresolved template tokens or malformed JSON.
Pro Tip
- -store the exact ARM request payload for failed runs and replay it in a sandbox to distinguish template bugs from environment drift quickly.
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 Azure services. Always validate implementation details against official provider documentation before deploying to production.