API contract monitoring

Detect API contract drift before integrations break

Monitor API and JSON endpoints with path-level diffs, JSON change detection, schema drift monitoring, incident closure, and automation-ready routing.

Smart Schema Validation (Pro): classify drift as schema_change, value_change, or mixed with severity
Policy rules and ignore paths suppress noise while escalating breaking endpoint changes

Monitor API View pricing

API diff details

Change| 2026-02-11 10:15:31 UTC

Accept baselineHide diff

Impact: Breaking schema change at /items/*/price

Classification: schema_change | Severity: high | Schema changes: 2 | Value changes: 1

Severity: Breaking only | Type: Schema | Path contains: /items/price

1010"id": "sku_238",

11--"price": 89.00,

-11+"price": "99.00",

-12+"currency": "USD",

Run details: engine=simple_fetch | status=200 | latency=210ms | requestId=req_9f8bc

How it works

Add critical GET endpoints and configure auth headers, retries, and fetch behavior

Canonicalize JSON and apply select/ignore paths so diffs represent contract changes, not payload noise

Use Smart Schema Validation (Pro) for schema/value classification and path-level severity

Changed runs open or update incidents using deterministic grouping

Acknowledge, resolve, or accept baseline when expected API rollouts land

Route alerts to email, webhook, Slack, or Teams with templates and policy rules

Use request IDs, run logs, and delivery attempts for fast debugging

What you get

Structured JSON evidence

Structured JSON evidence: changed paths, schema/value counts, top severity, and fingerprints

Incident lifecycle controls

Incident lifecycle controls: acknowledge, resolve, accept baseline with audit metadata

Policy automation

Policy automation: suppress, escalate, label, and route by classification/severity/path

Ops visibility

Ops visibility: status, latency, error context, request IDs, retry trace, and delivery history

What we monitor

Schema changes (type/required/shape) and value changes at stable JSON paths

Structured diff classification and severity (schema_change, value_change, mixed)

HTTP health context

HTTP health context: status codes, latency, retries/backoff, and failure categories

Secure request controls

Secure request controls: auth redaction, size/time limits, and SSRF protections

Breaking change examples

Removed field: customer.phone is removed from the response payload.
Type change: order.total changes from number to string.
Requiredness change: status becomes required where it was previously optional.

Use cases

Vendor API contract drift

Vendor API contract drift: catch breaking field/type changes before integration impact

Payments and billing endpoints

Payments and billing endpoints: detect regressions that can break checkout or reconciliation

Catalog/feed pipelines

Catalog/feed pipelines: track required field additions/removals before downstream failures

Post-deploy API validation

Post-deploy API validation: verify endpoint behavior and schema consistency after release

Incident response and audit

Incident response and audit: close the loop with baseline acceptance and logs

How DiffMon Compares to Common API Monitoring Approaches

Common API approaches

DiffMon

Uptime/status pings with limited change context

Contract drift detection with path-level JSON diffs

Raw payload snapshots without stable change classification

SSV classification + severity (schema_change, value_change, mixed)

Alerting without explicit closure semantics

Incidents, acknowledge/resolve, and baseline acceptance with audit trail

Fixed or manual notification fan-out

Policy rules to suppress, escalate, label, and route by path + severity

Custom scripts with brittle maintenance and weak observability

Managed runs, request IDs, retry history, and delivery attempt visibility

Why this matters

API drift silently breaks clients, jobs, and vendor integrations. Contract-level evidence with incident closure reduces MTTR and rework.

FAQ

Which alert channels are available by plan?

Free includes email alerts. Hobby and Pro include email plus signed webhooks.

What triggers an alert?

Canonical JSON hash changes or a detected change status

Is this just uptime monitoring?

No. Status is context; DiffMon is designed for contract drift and structured JSON change detection.

How often do you check?

Free: 24h, Hobby: 30m, Pro: 5m.

How are 429/5xx handled?

Retries with backoff; Retry-After is honored when present

How are payloads protected?

Responses are size-capped and timeouts enforced

Can I use auth headers?

Yes, stored securely and redacted from logs

What happens over limits?

Existing monitors keep running; new monitors are blocked

Is the platform safe?

SSRF protections block private IPs and metadata endpoints

Resources

API monitoring guide

Best practices for monitoring JSON endpoints

Read the guide

Guides

Browse API monitoring use cases and change patterns

Open guides

Pricing

Compare plans and monitor limits

View pricing

Smart schema validation

How DiffMon classifies API diffs into schema vs value changes, with severity, fingerprints, and troubleshooting.

Read docs

Related guides

Detect breaking API changes in production

How to detect schema drift, field removals, and type changes in third-party APIs before they break integrations.

Read guide

Monitor Third-Party Dependencies

How to monitor vendor APIs, status surfaces, legal pages, and pricing contracts before they break production workflows.

Read guide

Change detection vs visual regression testing

When structured diffs beat pixel diffs for monitoring third-party interfaces and production drift.

Read guide

Structured diffs, deterministic alerts, and automation-ready webhooks

Monitor API and JSON endpoints with path-level diffs, JSON change detection, schema drift monitoring, incident closure, and automation-ready routing.

Monitor API View pricing