API monitoring without the per-check taxUnlimited on every paid plan
HTTP checks run on lightweight persistent infrastructure — the marginal cost is near zero, so we don't charge per check. Define assertions, get timing breakdowns, and ship OTel insight packs from 14 locations.
monitors:
- name: Payment API
type: http
url: https://api.example.com/v1/payments
method: POST
frequency: 1m
locations: [us-east, eu-west, ap-southeast]
assertions:
- type: status_code
value: 200
- type: response_time
operator: less_than
value: 500
- type: json_body
path: $.status
value: healthy
How it works
HTTP check defined with assertions
Define your endpoint URL, method, headers, body, and assertions in YAML. No code required.
Runs from selected locations
Check executes from your configured locations at your configured frequency. Persistent infrastructure, zero cold-start latency.
Full timing breakdown + TLS inspection
DNS lookup, TCP connect, TLS handshake, TTFB, and content transfer timed separately. Certificate inspected.
OTel insight pack emitted
Timing phases, TLS details, assertion results, and anomaly scores emitted as a full OTLP insight pack.
Assertions on everything
Assert on status code, response time, JSON body fields, response headers, and body content. Chain multiple assertions — all must pass for the check to succeed.
status_codeequals 200response_timeless_than 500msjson_body$.status equals healthyheadercontent-type contains jsonbody_containsstring present in bodybody_not_containsstring absent from bodyassertions:
- type: status_code
value: 200
- type: response_time
operator: less_than
value: 500
- type: json_body
path: $.data.status
value: active
- type: header
name: content-type
operator: contains
value: application/json
- type: body_contains
value: "healthy"Full timing breakdown in OTel
DNS lookup, TCP connect, TLS handshake, TTFB, and content transfer timed separately and emitted as individual OTel metrics and span attributes. Anomaly-scored against 14-day baselines per location.
When your TLS handshake starts taking 3× longer, it shows up as a timing anomaly in your backend — not just a slow total response time that requires digging to diagnose.
synthetics.dns.lookup_durationsynthetics.tcp.connect_durationsynthetics.tls.handshake_durationsynthetics.http.ttfbsynthetics.http.content_transferTLS inspection built in
Certificate expiry, issuer chain, fingerprint, and days-until-expiry emitted as span attributes on every HTTPS check. Alert before a user sees a browser warning.
Configure your expiry alert threshold — get notified at 30 days, 14 days, or 7 days remaining. Not at zero, when it's already a user-facing problem.
# Emitted on every HTTPS check
synthetics.tls.valid true
synthetics.tls.expiry_days 42
synthetics.tls.valid_to 2026-05-15T00:00:00Z
synthetics.tls.issuer_cn Let's Encrypt
synthetics.tls.subject_cn api.example.com
synthetics.tls.fingerprint sha256:a1b2c3d4...
synthetics.tls.chain_valid true
synthetics.tls.handshake_duration 45Unlike per-check pricing models
Most tools charge per HTTP check per location per month. Unlimited means unlimited — define as many monitors as your infrastructure needs without a per-check budget conversation.
Every HTTP check emits a full OTel insight pack — timing phases, TLS details, and anomaly scores — not just response_time and pass/fail.
Fair use applies (500K hosted / 1M private per month). This covers hundreds of monitors running every minute across multiple locations.
Close your observability blind spot
Free tier includes 10,000 HTTP checks and 1,500 browser checks per month. No credit card required.
npx yorker init