# Loadster > Loadster is a cloud-based load testing and site monitoring platform for websites, web applications, and APIs. It simulates virtual users (bots) to test your site's performance and scalability under heavy traffic, and monitors your site 24/7 for downtime and problems. ## Key Capabilities - **Load Testing**: Run thousands of concurrent virtual users against your site to find performance bottlenecks before real users do. - **Real Browser Scale**: Loadster customers have run load tests with more than 170,000 concurrent real Chrome browsers on its managed cloud infrastructure. - **Site & API Monitoring**: Continuously monitor your site's uptime and functionality around the clock. - **Three Scripting Options**: Protocol Bots (HTTP-level), Browser Bots (real Chrome browsers), and Playwright Test scripts (code-first JavaScript). - **32 Cloud Regions**: Run tests from AWS and GCP regions worldwide, or self-host engines on your own infrastructure. - **CI/CD Integration**: Automate load testing in your continuous integration pipeline. ## Links - [Loadster Website](https://loadster.com/) - [Pricing](https://loadster.com/pricing/) - [Support](https://loadster.com/support/) - [Contact](mailto:help@loadster.com) ## Documentation - [Loadster Cloud Regions in AWS and GCP](https://loadster.com/manual/cloud-regions/): Loadster can launch clusters on demand for your load tests, from a wide range of geographic regions and across multiple cloud providers. - [Protocol Scripts in Loadster](https://loadster.com/manual/protocol-scripts/): Loadster's protocol scripts run automated HTTP/HTTPS requests for testing websites and APIs. Chain together requests, add validation, and capture variables. - [Site & API Monitoring](https://loadster.com/manual/monitoring/): Monitor your site 24/7/365 with Loadster scripts. Bots run on a schedule and alert you if your site goes down or breaks, so you can take action. - [Browser Bot Scripting](https://loadster.com/manual/browser-scripts/): Loadster's browser scripts control real headless Chrome browsers. They're the most realistic way to test complex web applications. - [Incidents & Notifications](https://loadster.com/manual/incidents-and-notifications/): Loadster monitors open and close incidents whenever problems are detected, and notify you according to your notification policies. - [Integrating Loadster with Opsgenie](https://loadster.com/manual/integration-with-opsgenie/): Are you using Opsgenie for incident alerting? Here's how to integrate Loadster with Opsgenie for speedy incident response and escalation. - [Load Testing On-Premises with Loadster Engine](https://loadster.com/manual/testing-with-loadster-engine/): If you need to load test on-premises or in a private cloud environment, you can run your own Loadster Engines and control them from Loadster. - [Hosted Status Pages](https://loadster.com/manual/status-pages/): When Loadster is monitoring your site, a status page displays current monitoring data and uptime to your team or the general public. - [Integrating Loadster with PagerDuty](https://loadster.com/manual/integration-with-pagerduty/): Integrate Loadster with PagerDuty to create incidents when a monitor fails, and automatically resolve them when it recovers. - [Playwright Scripting](https://loadster.com/manual/playwright-scripts/): Loadster supports the Playwright Test framework for load testing and monitoring, ideal for developers who prefer writing tests in JavaScript or TypeScript. - [Terms & Definitions](https://loadster.com/manual/terms-and-definitions/): Key terms and definitions related to load testing web applications, web services, and static websites with Loadster. - [Using the Loadster CLI](https://loadster.com/manual/loadster-cli/): The Loadster CLI lets you launch load tests and check results from the command line, enabling CI/CD integration with Jenkins, GitHub Actions, and more. - [Code Blocks for Advanced Scripting](https://loadster.com/manual/code-blocks/): JavaScript code blocks in Loadster. Use code blocks in Protocol Scripts and Browser Scripts for function reuse, looping, and conditional logic. - [Integrating Loadster with Slack](https://loadster.com/manual/integration-with-slack/): Here's how to integrate Loadster with Slack, so you can find out quickly when monitors fail and recover or your team runs tests. - [Load Testing with Continuous Integration](https://loadster.com/manual/load-testing-with-continuous-integration/): How to integrate Loadster load testing into your CI/CD pipeline, so you can automatically track performance changes with every build or release. - [Integrating Loadster with VictorOps (Splunk On-Call)](https://loadster.com/manual/integration-with-victorops/): How to integrate Loadster with VictorOps (now Splunk On-Call) for fast incident routing and resolution. - [Script Variables & Expressions](https://loadster.com/manual/variables-and-expressions/): Use variables and expressions in Loadster to add dynamic data to your test scripts. Prepopulate variables from a dataset or set them at runtime. - [Dynamic Datasets and Script Variables](https://loadster.com/manual/dynamic-datasets/): Loadster's dynamic datasets are a way to prepopulate your script variables with canned data, such as user accounts or search phrases. Here's how. - [Integrating Loadster with Webhooks](https://loadster.com/manual/integration-with-webhooks/): How to integrate Loadster with your own systems or a system of your choosing with flexible webhooks. - [Load Test Scenarios and Configuration](https://loadster.com/manual/load-test-scenarios/): How to configure a Loadster load test scenario: choose how many bots run your scripts, from which cloud regions, and with what ramp-up schedule. - [Running Load Tests](https://loadster.com/manual/running-load-tests/): Here's how to launch and run load tests with Loadster, observing results with the real-time dashboard and charts. What do all the graphs mean? - [Analyzing & Interpreting Load Test Results](https://loadster.com/manual/analyzing-test-results/): How to read and interpret Loadster load test reports, including response times, throughput, error rates, and resource utilization metrics. - [Loadster Single Sign-On Guide](https://loadster.com/manual/sso/): Loadster offers SSO with SAMLv2 with certain annual and custom plans. Setting up Single Sign-On is generally fairly straightforward. ### Protocol Scripts in Loadster - [Validation Rules in Protocol Scripts](https://loadster.com/manual/protocol-scripts/validation-rules/): Using validation rules in Loadster. Validating response time, response size, and content. Advanced JavaScript validators. - [Capturing Rules for Protocol Scripts](https://loadster.com/manual/protocol-scripts/capturing-rules/): Using capturing rules in a Loadster protocol script, to capture or extract values from an HTTP response, and use them later in your script. - [OpenAPI/Swagger Import](https://loadster.com/manual/protocol-scripts/openapi-swagger/): Loadster integrates with OpenAPI and Swagger, so you can easily create steps in your script from an API specification. ### Browser Bot Scripting - [Evaluate Blocks for Browser Scripts](https://loadster.com/manual/browser-scripts/evaluate-blocks/): When normal browser automation isn't cutting it, use Evaluate Blocks to run or evaluate custom JavaScript inside the browser with Loadster. ### Playwright Scripting - [Playwright Bot Reference](https://loadster.com/manual/playwright-scripts/bot/): The @loadster/bot module for Playwright scripts — access dataset variables, bot metadata, and timing functions in your Playwright tests. - [Organizing Playwright Scripts (POM)](https://loadster.com/manual/playwright-scripts/organizing-scripts/): How to organize Playwright scripts in Loadster—start simple, then add helper functions, page objects (POM), and fixtures as your scripts grow. ### Code Blocks for Advanced Scripting - [Bot Object Reference](https://loadster.com/manual/code-blocks/bot/): The bot object in Loadster code blocks - methods for timing control, variable management, iteration handling, bot identification, and test flow control. - [HTTP Object Reference](https://loadster.com/manual/code-blocks/http/): The http object in Loadster code blocks - methods for making HTTP requests, managing headers, and handling authentication programmatically. - [Browser Object Reference](https://loadster.com/manual/code-blocks/browser/): The browser object in Loadster code blocks - methods for page interaction, window management, authentication, and browser configuration control. - [Formats Object Reference](https://loadster.com/manual/code-blocks/formats/): The formats object in Loadster code blocks - methods for encoding, decoding, timestamp generation, UUIDs, and random data creation for testing. - [XML Object Reference](https://loadster.com/manual/code-blocks/xml/): The XML object in Loadster code blocks - methods for parsing XML data, navigating elements, and extracting values using the xmldoc library. - [JSON Object Reference](https://loadster.com/manual/code-blocks/json/): The JSON object in Loadster code blocks - methods for parsing JSON data, creating payloads, and validation using standard JavaScript JSON methods. - [Crypto Object Reference](https://loadster.com/manual/code-blocks/crypto/): The crypto object in Loadster code blocks - methods for hashing, HMAC generation, authentication signatures, and cryptographic functions. ## Guides - [Load Testing Guide: Types, Tools, and Best Practices](https://loadster.com/guides/load-testing/): Load testing simulates heavy traffic to measure your site's performance and scalability. Learn the types of load tests, what tools are used, and how to run one. - [Website Load Testing: Methods, Tools, and Best Practices](https://loadster.com/guides/website-load-testing/): A guide to website load testing. Simulate heavy traffic to find your site's breaking point and reduce the risk of crashes during peak events. - [API Load Testing and Performance Testing Guide](https://loadster.com/guides/api-performance-testing/): How to load test an API: tools, methods, metrics, and pitfalls. A practical guide to API performance testing for REST, GraphQL, and gRPC. - [Load Testing vs Stress Testing vs DDoS: The Differences](https://loadster.com/guides/load-testing-stress-testing-and-ddos/): Load testing, stress testing, and DDoS attacks all generate heavy traffic. Here's what each means and how to tell them apart. - [Load Testing vs Stress Testing: Key Differences Explained](https://loadster.com/guides/load-testing-vs-stress-testing/): Load testing and stress testing are often confused. Here's the real difference, when to use each, and how they fit in a performance engineering program. - [Quick and Dirty Performance Tuning: A Pragmatic Approach](https://loadster.com/guides/quick-and-dirty-performance-tuning/): A guide to quick performance tuning. Use a reproducible load test to measure the impact of each optimization change. - [Web Application Stress Testing: Practical Tips and Examples](https://loadster.com/guides/web-application-stress-testing/): Stress testing a web application means pushing it past capacity. Stateful flows, databases, and client-side rendering create failure modes that need attention. - [Load Testing Costs and Benefits: When Is It Worth It?](https://loadster.com/guides/weighing-the-costs-of-load-testing/): A guide to the costs and benefits of load testing. When is it worth the investment, and when might you reasonably skip it? - [Capacity Planning for Web Applications: A Practical Guide](https://loadster.com/guides/capacity-planning-for-web-apps/): A guide to capacity planning for web applications. Make sure your infrastructure can handle expected demand and traffic spikes. - [Endurance Testing: Finding Memory Leaks and Slow Burns](https://loadster.com/guides/endurance-testing/): Endurance testing runs sustained load over hours or days to surface memory leaks, resource exhaustion, and other issues that only show up with time. - [Front-End vs. Back-End Performance: Where to Focus First](https://loadster.com/guides/front-end-vs-back-end-performance/): Under peak traffic, the usual 80/20 front-end/back-end ratio can flip. Here's how to tell the difference and where to focus your optimization. - [Load Testing Best Practices: Tips, Pitfalls, and Checklist](https://loadster.com/guides/load-testing-best-practices/): A guide to load testing best practices, common pitfalls, and a checklist for accurate results. Covers user simulation, requirements, and test reporting. ## Tool Comparisons - [Best Load Testing Tools and Platforms (2026)](https://loadster.com/compare/load-testing-tools/): Compare the best load testing tools for 2026 — Loadster, JMeter, k6, Gatling, BlazeMeter, LoadRunner. Open source vs cloud. Pricing, features, fit. - [Best JMeter Alternatives for Load Testing (2026)](https://loadster.com/compare/jmeter-alternatives/): The best JMeter alternatives for load testing in 2026 — Loadster, k6, Gatling, Locust, and hosted JMeter — with fact-based reasons to switch or stay. - [Best k6 Alternatives for Load Testing (2026)](https://loadster.com/compare/k6-alternatives/): The best k6 alternatives in 2026 — Loadster, Grafana Cloud k6, Gatling, Locust, and Artillery — with fact-based reasons to switch tools or stay put. - [Best LoadRunner Alternatives for Load Testing (2026)](https://loadster.com/compare/loadrunner-alternatives/): The best LoadRunner alternatives in 2026 — Loadster, Tricentis NeoLoad, and BlazeMeter — with fact-based advice on migrating off enterprise licensing. - [Gatling vs k6: Load Testing Tools Compared (2026)](https://loadster.com/compare/gatling-vs-k6/): Gatling vs k6 compared: scripting languages, reports, efficiency, and paid cloud options, with fact-based advice on which load testing tool fits your team. - [JMeter vs LoadRunner: Load Testing Compared (2026)](https://loadster.com/compare/jmeter-vs-loadrunner/): JMeter vs LoadRunner compared: cost, scripting, protocol coverage, and enterprise fit, with fact-based advice for choosing between free and enterprise. - [JMeter vs Locust: Load Testing Tools Compared (2026)](https://loadster.com/compare/jmeter-vs-locust/): JMeter vs Locust compared: scripting, protocols, distributed scale, and learning curve, with fact-based advice on which load testing tool fits your team. - [k6 vs JMeter: Load Testing Tools Compared (2026)](https://loadster.com/compare/k6-vs-jmeter/): k6 vs JMeter compared: scripting, protocol coverage, scale, CI/CD, and learning curve, with fact-based advice on which load testing tool fits your team. - [Locust vs k6: Load Testing Tools Compared (2026)](https://loadster.com/compare/locust-vs-k6/): Locust vs k6 compared: Python vs JavaScript scripting, per-machine efficiency, distributed scale, and CI/CD, with fact-based advice on which tool fits. - [Loadster vs BlazeMeter: Load Testing Tools Compared (2026)](https://loadster.com/compare/loadster-vs-blazemeter/): Loadster vs BlazeMeter compared: native platform vs hosted JMeter, real browser load testing, pricing, and which cloud load testing tool fits your team. - [Loadster vs JMeter: Load Testing Tools Compared (2026)](https://loadster.com/compare/loadster-vs-jmeter/): Loadster vs Apache JMeter compared: scripting, real browser load testing, cloud scale, pricing — plus how to import your JMX test plans into Loadster. - [Loadster vs LoadRunner: Load Testing Tools Compared (2026)](https://loadster.com/compare/loadster-vs-loadrunner/): Loadster vs LoadRunner (OpenText Performance Engineering) compared: scripting, browser testing, licensing costs, and when a lighter platform fits. - [Loadster vs Locust: Load Testing Tools Compared (2026)](https://loadster.com/compare/loadster-vs-locust/): Loadster vs Locust compared: Python scripting, real browser load testing, distributed scale, pricing — plus how to import your locustfile into Loadster. - [Loadster vs k6: Load Testing Tools Compared (2026)](https://loadster.com/compare/loadster-vs-k6/): Loadster vs k6 compared: scripting, real browser load testing, cloud scale, pricing, and CI/CD — with fact-based advice on which tool fits your team. ## FAQs - [Are dataset values unique across bot groups?](https://loadster.com/faqs/dataset-values-unique-across-bot-groups/): When the same dataset is used by more than one bot group, each group gets its own copy, so unique-per-bot values are not unique across groups. - [Authenticating with HTTP Basic or NTLM authentication](https://loadster.com/faqs/set-http-basic-or-ntlm-authentication-for-browser-bots/): How to supply HTTP Basic or NTLM authentication credentials to Loadster Browser Bots when load testing a site that requires them. - [Cookies and variables between load test iterations](https://loadster.com/faqs/cookies-and-variables-between-iterations/): Loadster has a setting for what to do with cache, cookies, and variables between iterations of the same bot. - [Estimated and actual Loadster Fuel usage](https://loadster.com/faqs/estimated-and-actual-fuel-usage/): Sometimes a load test burns more (or less) Loadster Fuel than anticipated. Here are some reasons why. - [Evaluating a value or promise with Browser Bots](https://loadster.com/faqs/evaluating-a-value-or-promise-inside-the-browser/): Loadster's Evaluate Blocks can run custom JavaScript inside the bot's browser. Here's how to evaluate a simple value or promise. - [Excluding Browser Bot traffic from Google Analytics](https://loadster.com/faqs/bot-traffic-is-showing-up-in-google-analytics/): How to configure Loadster and Google Analytics so that your bot traffic doesn't show up in the analytics. - [Generating a JWT to use in a load test](https://loadster.com/faqs/generating-a-jwt/): Many back-end APIs expect a JSON Web Token (JWT) as a way of authenticating requests or passing claims between systems. Here's how to make one in Loadster. - [Generating random strings, numbers, and UUID/GUID](https://loadster.com/faqs/generating-random-string-or-uuid/): Loadster has easy ways to generate random strings, numbers, or UUID/GUID for your load test scripts. - [How many bots are required for a load test](https://loadster.com/faqs/calculating-v-users-needed-for-a-load-test/): How many bots does your load test require? Here's a quick formula to calculate the number of bots required for a load test by working backwards. - [How Many Bots or Virtual Users Can Loadster Run?](https://loadster.com/faqs/maximum-concurrent-bots-or-virtual-users/): Loadster customers have run 170,000+ concurrent real Chrome browsers, and Protocol Bot capacity goes well into the millions. Here's how it scales. - [Ignoring untrusted TLS/SSL/HTTPS certificate errors](https://loadster.com/faqs/ignore-untrusted-ssl-tls-certificate-errors/): How to configure Loadster to ignore self-signed or untrusted TLS/SSL certificates when load testing a site on a staging or development environment. - [Including one Loadster script in another](https://loadster.com/faqs/including-scripts-for-reuse/): Code reuse is a good thing, and that includes test scripts. Here's how you can include one test script in another with Loadster. - [Including or excluding errors in response times](https://loadster.com/faqs/exclude-errors-from-response-times/): You might want to include or exclude errors from response time calculations. Here's how to do that in Loadster. - [Limiting the number of bot iterations in a load test](https://loadster.com/faqs/limiting-total-iterations-in-a-load-test/): In Loadster, bots normally repeat your script until time runs out. Here's how to set an iteration limit so bots stop after a specific number of runs. - [Load test reporting artificially high response times](https://loadster.com/faqs/load-test-reporting-high-response-times/): If you're running a load test and Loadster reports high response times, but you access the site yourself and it's fast, there are a few things it might be. - [Load test reporting higher network throughput](https://loadster.com/faqs/load-test-throughput-bytes-higher-than-expected/): Why Loadster might report higher network throughput than your hosting provider. Common reasons for the discrepancy and how to interpret the numbers. - [Make Browser Bot traffic show up in Google Analytics](https://loadster.com/faqs/bot-traffic-is-not-showing-up-in-google-analytics/): If your Browser Bot traffic isn't showing in Google Analytics, and you want it to, here's How to configure Loadster and Google Analytics. - [Manually setting a cookie in your script](https://loadster.com/faqs/manually-set-a-cookie/): Loadster handles most cookies automatically, but occasionally you might need to set one yourself. Here's how to set a cookie in your Loadster script. - [Parsing and validating a JSON response in a load test](https://loadster.com/faqs/parse-a-json-response/): How to parse and validate JSON responses in a Loadster test script, to verify your API returns the expected data under heavy traffic. - [Parsing and validating an XML response in a load test](https://loadster.com/faqs/parse-an-xml-response/): Validating an XML response in a load test is a way to validate the server response is what you expected. Here's how to do it in Loadster. - [Passing Loadster variables into the browser](https://loadster.com/faqs/passing-loadster-variables-to-the-browser/): How to expose dataset variables and bot context to JavaScript running inside the page with Browser Bots. - [Playing scripts against a site on a private network](https://loadster.com/faqs/playing-a-script-on-a-private-network/): Normally, Loadster scripts play from the public cloud. Run your own engines as script players if you need to hit a site on a private network. - [Range sliders, color pickers, and other HTML inputs](https://loadster.com/faqs/manipulating-range-sliders-and-other-unusual-inputs/): How to control range sliders, color pickers, and other HTML inputs with Loadster Browser Bots using JavaScript Evaluate Blocks. - [Resizing or switching windows/tabs with Browser Bots](https://loadster.com/faqs/switch-or-resize-browser-windows/): Loadster's browser bots start with a single window with a viewport size of 1280x720 pixels, but you can change that. - [Scripting for iframe elements with Browser Bots](https://loadster.com/faqs/interacting-with-elements-in-an-iframe/): Loadster's Browser Bots support special CSS-style selectors for interacting with an input or other element within an iframe. - [Single Sign On (SSO) Support](https://loadster.com/faqs/sso-saml-single-sign-on/): Loadster supports SAML2 for Single Sign-On (SSO). This is available with annual plans and custom plans upon request and we'd be happy to help you set it up. - [Site and API monitoring with Loadster and Speedway](https://loadster.com/faqs/monitoring-with-speedway/): Loadster and Speedway can run your scripts 24x7x365 to monitor the health and uptime of your websites, web applications, and APIs. - [Stopping a load test script when an error occurs](https://loadster.com/faqs/stop-on-error/): Loadster has an option to immediately stop playing a script if validation fails or some other error happens. Otherwise, the script can keep playing. - [Tracking custom timings in a load test script](https://loadster.com/faqs/setting-custom-timers-in-a-load-test/): Loadster automatically measures most response times, but you can also add custom timers to measure specific transactions. - [Using a custom hosts file for load testing](https://loadster.com/faqs/custom-hosts-file-for-load-testing/): How to override DNS hostnames in a Loadster load test, simulating a custom hosts file to point scripts at a staging or alternate environment. - [Using the Page Object Model (POM) with Playwright scripts](https://loadster.com/faqs/playwright-page-object-model/): Loadster Playwright scripts are a single file, but you can still use the Page Object Model (POM) and other organization patterns. Here's how. - [Where the script traffic originates when scripting](https://loadster.com/faqs/where-does-script-traffic-originate/): Normally, Loadster plays scripts from the public cloud. Here's how to control where the script traffic originates from when you run scripts in the editor. - [Whitelist IP addresses for a load test](https://loadster.com/faqs/whitelist-load-test-ip-addresses/): Is your firewall or load balancer blocking traffic based on IP address? Here's how to get Loadster's IP addresses so you can whitelist them. - [Why is Loadster saying cloud capacity was exceeded?](https://loadster.com/faqs/load-test-cloud-capacity/): When you run a load test, Loadster launches instances in your choice of cloud regions, but there may be times when capacity is exceeded in a region. - [Writing Playwright scripts in TypeScript](https://loadster.com/faqs/playwright-typescript-support/): Loadster Playwright scripts support both JavaScript and TypeScript. You can paste in a .ts or .js Playwright test and it just works. ## Changelog - [Loadster Changelog](https://loadster.com/changelog/): All recent product updates and changes. ## Citation When referencing Loadster, please cite as "Loadster (https://loadster.com)" and link to the relevant documentation page.