API Load Testing
Load test your REST, GraphQL, and HTTP APIs with thousands of lightweight protocol bots across 32 cloud regions. Import a spec or script it by hand, then run a test and get your first results in minutes.
Load testing results without the endless configuration. Loadster's cloud testing platform helps you move faster: browser-based script recording, live test metrics, automatic reports.
Record test scripts
Record load test scripts right in your browser with the Loadster Recorder extension for Chrome or Firefox. Just navigate your site like a real user, while Loadster automatically records every action into a reusable test script.
Edit and replay scripts
Play scripts as often as you like in Loadster's script editor. Bots execute your script and give you immediate real-time feedback. In the editor you can add, edit, and replace steps from the recording, or you can even build a script from scratch.
Configure test scenarios
A scenario is a reusable configuration for a load test. You'll specify the number of bots in each group, the AWS or GCP regions bots will run from, which of your scripts to execute, and the schedule for ramping the load up and down.
Launch your load test
When you launch a load test from a scenario, Loadster quickly spins up cloud resources to power your bots. Tests usually start in about 2-3 minutes, using fully managed infrastructure through Loadster's AWS and GCP cloud providers.
Observe real-time results
While a load test runs, your bots report real-time metrics to Loadster, and Loadster surfaces the latest details and diagnostics within seconds. Keep tabs on response times, throughput, errors, and detailed traces so you can see how your site is performing under load.
Generate test reports
After a load test finishes, Loadster automatically creates a detailed report so you can review your site's performance and scalability. This includes detailed graphs showing response times, errors, network and transaction throughput, and more. The report also includes detailed traces with request and response bodies or screenshots to help with troubleshooting.
Repeat and iterate
Load testing is an iterative process, and it's rare that everything goes perfectly on the very first try. After all, the point of the test is to discover scalability bottlenecks so you can fix them instead of crashing in production. With Loadster you can quickly re-test a previous scenario, or make changes to your scripts or scenarios and run again at any time.
Protocol Bots, built for APIs. Lightweight HTTP clients that push high throughput at low cost.
API load testing doesn't need a browser. Loadster's Protocol Bots send requests straight at the HTTP layer, so each bot is cheap to run and can drive a high request rate. That makes Protocol Bots ideal for REST and GraphQL APIs, microservices, and high-throughput endpoints, where you care about requests per second, latency, and error rates rather than rendering a page.
Testing a browser-based front end too? Loadster also runs real-browser Playwright and Browser Bots, and you can mix bot types in a single test to model a complete system end to end.
Start from your OpenAPI spec, or script it yourself. Turn an API definition into a load test in minutes.
Already have an OpenAPI (Swagger) definition? Loadster can generate a protocol script from it, so you don't have to write every request by hand. From there you parameterize requests, add authentication, and chain calls into realistic workflows.
Real API workloads are rarely a single endpoint hit in a loop. Protocol scripts let you log in and capture a token, feed unique values from a dataset into each bot, extract values from one response with code blocks and pass them to the next request, and assert on status codes and response bodies — so every bot behaves like a different real client.
Measure latency, throughput, and errors under load. Live metrics from every bot, aggregated in real time.
Loadster reports response times with full percentiles (50th, 90th, 95th, and 99th), requests per second, and error rates for every endpoint in your script, updating live as the test runs. When throughput plateaus while concurrency keeps climbing, or the 99th percentile starts to spike, you've found the point where your API begins to strain — and traces on failed requests show you the exact call and response that broke.
One script for load testing, stress testing, and monitoring. Write your API test once and reuse it.
The same protocol script can drive a full-scale load test, a stress test that pushes your API past its breaking point, or a 24/7 API monitor that runs on a schedule and alerts you the moment an endpoint slows down or starts returning errors.
Run API load tests in your pipeline. Catch performance regressions on every deploy.
The Loadster CLI runs from any CI environment — GitHub Actions, GitLab CI, Jenkins, CircleCI — so an API load test can run automatically on every pull request or deploy. Encode response time and error rate thresholds in the scenario, and the job fails automatically when your API regresses.
Load test your API from 32 cloud regions across AWS and GCP clouds. Monitor from 8 dedicated locations on 5 continents.
Loadster scales with your testing and your budget. Choose between flexible pay-as-you-go and subscription pricing.
Monthly Fuel Plans
Starting at $78 a month
Subscribe to a monthly plan to automatically add fuel every month at a discount. Unused fuel rolls over as long as you keep the plan.
Plan PricingPay As You Go
Starting at $97 for 1000 units
Purchase as much Loadster Fuel as you need for your load testing and monitoring. No commitment, just buy it when you need it.
Fuel PricingLoadster has improved the performance, scalability, and uptime of thousands of sites. We're proud to be of service to the best teams.
Move fast
Don’t crash
Ready to cut your risk of downtime? Load test to prevent crashes. Monitor to react quickly.