Performance testing

Fast, and still fast under load.

API suites, load tests and PageSpeed, aimed only at a domain you have verified. Monitors watch between runs, and alerts go to Slack, Teams or a signed webhook.

Test performance free Real-user monitoring

Capabilities
Use cases
Benefits
Works with
FAQ

Search studies, sessions, themes…AI chat

← PerformanceStorefront✓ shop.example.com · verifiedproductionstaging

SuitesEnvironments & domainsRequests & loadReal usersMonitoring & alerts

LCP · p752.1 s Good · 1,240 real visits

Checkout API14/15 Passed · 3 min ago

Monitors3 of 3 up certificates valid

Alerts1 firing Slow INP → Slack

LCP p75production · real visits1 h6 h24 h72 h7 d

3.0 s2.5 s2.0 s1.5 s

good ≤ 2.5 sv2.4.0v2.4.1v2.4.2

6 Oct8 Oct10 Oct12 Oct

SuitesNew suite

Checkout APIAPI · Every hour14/15Passed

Storefront pagesPageSpeed · Every day12 pagesPassed

Account APIAPI · Every 6 hours9/9Passed

Alerts4 rules

Slow INPINP p75 above 200 ms · productionFiring

Slack sent today, 09:12Checkout API downOKStaging certificateOKCheckout API suiteOK

StorefrontSuitesEnvironments & domainsRequests & loadReal usersMonitoring & alerts

EnvironmentsAdd environment

production Receiving datahttps://shop.example.com

staging Not installed yethttps://staging.shop.example.com

Where a request may go✓A domain this workspace proved it owns✕The Live URL snippet, as proof✕A private or internal address✕Wherever a redirect points

DomainsVerify another domain

✓shop.example.comand every subdomain under itVerifiedDNS record · 2 Oct

Ways to prove a domain

DNS recordA TXT record at the domainFile on the site/.well-known/utestme-verify.txtA teammate’s emailConfirmed, at that domain

Add this TXT recordutestme-verify=Copy✓ Found on 2 Oct — verified

verified domains only

Load testPOST /api/cartproductionPassedCompare withStart load test

ShapeA number of requestsSteady loadStagedRamp up, hold, downSpikeSteps

Preview20 at once0 s60 s120 s

StageSecondsTo at once13020260203300Pass / failMax p95400 msMax errors1 %Min throughput80/s

Second by second requests/s p95 at once failedRequests9,480Throughput105/sp95268 msErrors0.2 %Peak at once200 s30 s90 s120 s

VerdictPassed✓p95 268 ms≤ 400 ms✓Errors 0.2 %≤ 1 %✓105/s≥ 80/s

Compare with8 Oct → todayMetricBeforeAfterChangep95412 ms268 ms−35 %BetterThroughput88/s105/s+19 %BetterErrors0.9 %0.2 %−78 %Betterp50160 ms151 ms−6 %No change

a load test · sample project

Verified domains only: Every request goes to a domain your workspace proved it owns. A load test cannot be aimed at anyone else’s server.
One signed-in session: A suite signs in once at the top. Every scenario after it reuses the token or cookies that login captured.
Load you can shape: A fixed count, steady load, or ramp, spike and step stages — with a pass/fail verdict when you set thresholds.
Alerts where the team already is: Slack, Microsoft Teams or a signed webhook. Every alert records when it fired and when it resolved.

Core capabilities

Is it fast, and does it hold up?

Pick a capability to see it drawn from a sample project.

A POST to your login path captures the token or cookies, and the scenarios after it reuse them, in order. “Discover endpoints” reads your OpenAPI file, robots.txt and sitemaps — or paste a request from your browser. A p95 and a fail-rate threshold make each run Passed or Failed.

Checkout APIAPI suiteproduction · shop.example.comDiscover endpointsPaste from your browserRun suite

API run · 3 min agoPassed14/15 passedp50 142 msp95 388 ms2.9 s total#ScenarioStatusTime

1POST/api/logintoken captured · …k3Fz200212 ms✓

2GET/api/accountreuses the session20096 ms✓

3GET/api/products?category=shoes200184 ms✓

4POST/api/cart201238 ms✓

5POST/api/cart/couponexpected 200422120 ms✕

6GET/api/cart20088 ms✓

7GET/api/shipping/options200142 ms✓

8POST/api/checkout/address200176 ms✓

9POST/api/checkout/quote200388 ms✓

10GET/api/orders/latest200118 ms✓

✓ 5 more scenarios, all passed

One signed-in sessionPOST /api/login→token + cookie→14 scenariosCapturedtoken …k3Fz from body.token · cookie sessionStoredSealed — only the four-character hint is shown

Thresholds✓p95 at most 800 ms388 msPassed✓Fail if more than 10 % of scenarios fail6.7 %Passed

SlowestPOST /api/checkout/quote388 msPOST /api/cart238 msPOST /api/login212 msGET /api/products?category=shoes184 msPOST /api/checkout/address176 ms

Run automatically next run 11:0015 min30 min1 h3 h6 h12 hDaily

an API suite run · sample project

Common use cases

Where it slows down

Usually under load, after a release, or on the day a certificate runs out.

Load testPOST /api/cartproductionPassedCompare withStart load test

ShapeA number of requestsSteady loadStagedRamp up, hold, downSpikeSteps

Preview20 at once0 s60 s120 s

StageSecondsTo at once13020260203300Pass / failMax p95400 msMax errors1 %Min throughput80/s

Second by second requests/s p95 at once failedRequests9,480Throughput105/sp95268 msErrors0.2 %Peak at once200 s30 s90 s120 s

VerdictPassed✓p95 268 ms≤ 400 ms✓Errors 0.2 %≤ 1 %✓105/s≥ 80/s

Compare with8 Oct → todayMetricBeforeAfterChangep95412 ms268 ms−35 %BetterThroughput88/s105/s+19 %BetterErrors0.9 %0.2 %−78 %Betterp50160 ms151 ms−6 %No change

before → after · sample project

Before a launch

Load test the checkout API before the traffic does

Ramp to the load you expect, hold it, and set a p95 and an error budget. Fix what fails, run it again and compare the two runs side by side.

Checkout APIAPI suiteproduction · shop.example.comDiscover endpointsPaste from your browserRun suite

API run · 3 min agoPassed14/15 passedp50 142 msp95 388 ms2.9 s total#ScenarioStatusTime

1POST/api/logintoken captured · …k3Fz200212 ms✓

2GET/api/accountreuses the session20096 ms✓

3GET/api/products?category=shoes200184 ms✓

4POST/api/cart201238 ms✓

5POST/api/cart/couponexpected 200422120 ms✕

6GET/api/cart20088 ms✓

7GET/api/shipping/options200142 ms✓

8POST/api/checkout/address200176 ms✓

9POST/api/checkout/quote200388 ms✓

10GET/api/orders/latest200118 ms✓

✓ 5 more scenarios, all passed

One signed-in sessionPOST /api/login→token + cookie→14 scenariosCapturedtoken …k3Fz from body.token · cookie sessionStoredSealed — only the four-character hint is shown

Thresholds✓p95 at most 800 ms388 msPassed✓Fail if more than 10 % of scenarios fail6.7 %Passed

SlowestPOST /api/checkout/quote388 msPOST /api/cart238 msPOST /api/login212 msGET /api/products?category=shoes184 msPOST /api/checkout/address176 ms

Run automatically next run 11:0015 min30 min1 h3 h6 h12 hDaily

a scheduled suite run · sample project

After a deploy

A scheduled suite notices before a customer does

The checkout suite runs every hour as a signed-in shopper. When a release breaks a route, that scenario fails its status check; past your fail-rate threshold, the run fails and the alert goes out.

Real-user monitoringWhat your visitors measured after the same deploy.

StorefrontSuitesEnvironments & domainsRequests & loadReal usersMonitoring & alertsAdd monitor

HomepageGET https://shop.example.comEvery 1 minUpUptime, 24 h100.00%0 failed of 1,440Response p50 / p95182 ms / 340 msCertificateValid · 64 daysSince 09:51 · No failed checks · last 60 checksResponse time

Checkout APIGET https://shop.example.com/api/healthEvery 15 minUpUptime, 24 h97.9%2 failed of 96Response p50 / p9596 ms / 210 msCertificateValid · 64 daysSince yesterday, 20:00 · 2 failed · last 60 checks

StagingGET https://staging.shop.example.comEvery 5 minUpUptime, 24 h100.00%0 failed of 288Response p50 / p95240 ms / 410 msCertificateValid · 87 daysSince 05:55 · No failed checks · last 60 checks

AlertsNew alertSlow INPINP p75 above 200 ms · SlackFiringCheckout API down2 failed checks in a row · TeamsOKStaging certificateexpires within 14 days · WebhookOKCheckout API suitea run fails · SlackOKSend toSlackMicrosoft TeamsSigned webhook

Alert historyFiredSlow INPSlack senttoday, 09:12ResolvedCheckout API downTeams sentyesterday, 23:00FiredCheckout API downTeams sentyesterday, 22:45ResolvedStaging certificateWebhook sent · signed3 OctFiredStaging certificateWebhook sent · signed1 Oct

monitors and alert history · sample project

Before a certificate lapses

Renew the certificate before the browser warns anyone

A monitor reads the certificate every six hours. The alert fires inside the number of days you chose, and resolves once the new certificate is in place.

Benefits

Numbers you can act on

412 ms268 msp95, before → after · sample project
Before and after, measured
Compare a load test with an earlier one. A change under 10 % is called no change, and a different URL or load gets a warning.
PassedFailed
A verdict when you ask for one
Set thresholds and a run comes back Passed or Failed. Set none and you get the numbers without a verdict.
2failed checks in a row before “down”
Down means down
One dropped check does not wake anyone. Two in a row does, and the alert resolves when the monitor is back.

Works with what you have

Your API, your browser, your channels

Nothing to rewrite before the first run.

OpenAPI, robots.txt and sitemaps

“Discover endpoints” reads them and suggests the scenarios and pages to test.

Your browser’s DevTools

Paste the request headers, or a request copied as cURL. Credentials are sealed, and only a four-character hint is ever shown.

Slack, Teams or a signed webhook

Where alerts go. Email is not one of them.

Your verified domain

Proved by a DNS TXT record, a file on the site, or a teammate’s confirmed email at that domain.

Discover more

The rest of the pillar, and beside it

FAQ

What a backend lead asks first

Why do I have to verify my domain?

A load test is a burst of traffic at a server, so every request goes only to a domain your workspace proved it owns: a DNS TXT record, a file at /.well-known/utestme-verify.txt, or a teammate’s confirmed email at that domain. The Live URL script snippet does not count as proof.

Can I load-test someone else’s site?

No. Requests go only to verified domains, private addresses are refused at the socket, and a test request never follows a redirect.

Where do alerts go?

To Slack, Microsoft Teams or a signed webhook. Not email. Each alert is recorded when it fires and again when it resolves.

How big can a load test get?

Up to 50 requests at once, and 10,000 requests or 3600 seconds per test. A suite holds up to 100 scenarios and a PageSpeed suite up to 40 pages. A workspace runs 5 performance jobs at once and keeps up to 50 monitors.

The tester app

Test from your pocket

The uTestMe tester app runs a study on a phone. Taps and screens recorded, consent first, results in the same view.

Coming soon onApp StoreGet it onGoogle Play

Scan to install

Tap tracking
Screen recording
Consent first

Test code · K7F2-9QA