Dev

Fake Browser Cookie Generator

A fake browser cookie generator gives developers ready-made HTTP cookie strings without the tedium of constructing each attribute by hand. Realistic cookies require more than a name and value: they need properly formatted expiry timestamps, domain and path attributes, and security flags like HttpOnly, Secure, and SameSite. Getting all of those right manually — especially when you need dozens of them for load tests or parser fuzz tests — is error-prone and slow. This generator produces syntactically valid cookie headers you can drop straight into Postman, curl commands, browser DevTools, or test fixture files. Each generated cookie randomizes the name, value, expiry date, domain, and path, mirroring the variety you'd encounter in real production traffic. The Secure and HttpOnly flags are included or omitted based on your selection, so you can test both hardened and legacy cookie configurations. Cookie handling bugs are among the most common sources of authentication bypasses and session fixation vulnerabilities. Having a fast supply of well-formed dummy cookies lets you exercise edge cases in middleware, validate your cookie-parsing library against unexpected inputs, and populate mock sessions without spinning up a live backend. Security researchers use similar synthetic cookies when building controlled lab environments for CSRF and XSS research. Set the count to match the volume your scenario requires — a handful for a quick unit test, or fifty-plus for stress-testing a parser — then toggle the security flags to match your target environment. Copy the output directly into your test suite, HTTP client, or exploit framework and skip the formatting guesswork entirely.

How to Use

  1. Set the Number of Cookies field to the quantity your test scenario requires.
  2. Choose Yes or No in the Secure/HttpOnly toggle to match your target cookie configuration.
  3. Click Generate to produce a fresh batch of randomized, properly formatted cookie strings.
  4. Copy individual cookies or the full list into your HTTP client, test fixture, or script.

Use Cases

  • •Fuzz-testing a custom HTTP cookie parser with varied inputs
  • •Populating Postman or Insomnia pre-request scripts with session cookies
  • •Writing unit tests for middleware that validates cookie attributes
  • •Simulating multi-user sessions in Playwright or Cypress end-to-end tests
  • •Generating fixture data for authentication logic integration tests
  • •Building controlled lab environments for CSRF or XSS security research
  • •Testing cookie-jar behavior in HTTP client libraries like axios or requests
  • •Reproducing cookie overflow edge cases in penetration testing exercises

Tips

  • →Generate cookies without Secure/HttpOnly flags when testing legacy code paths or local HTTP-only dev servers that reject strict cookies.
  • →Combine multiple generated cookie strings into a single Cookie: header line separated by semicolons to simulate realistic multi-cookie browser requests.
  • →Use a count of 50 or more to stress-test parser performance and check whether your application silently drops cookies beyond a per-domain limit.
  • →Paste generated cookies into browser DevTools under Application > Cookies to manually inject sessions into a running app without writing any code.
  • →When writing Playwright tests, load generated cookies via context.addCookies() to pre-authenticate test users without going through the login UI each time.
  • →Cross-check generated cookie names against your application's expected cookie names to write negative tests confirming unknown cookies are safely ignored.

FAQ

What does a valid HTTP Set-Cookie header look like?

A valid Set-Cookie header includes a name=value pair followed by optional attributes separated by semicolons: for example, sessionId=abc123; Path=/; Domain=example.com; Expires=Wed, 01 Jan 2026 00:00:00 GMT; HttpOnly; Secure. This generator produces strings in exactly that format so you can paste them directly into request headers or test fixtures.

What does the HttpOnly flag do on a cookie?

HttpOnly tells the browser to block JavaScript access to that cookie via document.cookie. This mitigates XSS attacks where injected scripts would otherwise steal session tokens. Generating cookies both with and without this flag lets you test that your application correctly enforces HttpOnly on sensitive cookies and rejects attempts to read them client-side.

What is the Secure flag on a cookie?

The Secure flag instructs the browser to send the cookie only over HTTPS connections, never plain HTTP. When testing locally without TLS, you may need to disable this flag — which is why this generator lets you toggle it. Testing both states helps you confirm your application handles the flag correctly across development and production environments.

Can I use these generated cookies to log in to a real website?

No. The values are randomly generated strings with no relationship to any live server's session store. Submitting them to a real application will result in rejection or a new session being created. These cookies are strictly for testing parsers, middleware, and mock environments where the server-side validation is either absent or under your control.

What is the SameSite cookie attribute and which value should I test?

SameSite restricts when a cookie is sent with cross-site requests. Strict blocks all cross-site sending; Lax allows it on top-level GET navigations; None sends it always but requires Secure. Testing all three values is worthwhile because browsers enforce SameSite differently, and your CSRF protections or OAuth redirect flows may behave unexpectedly depending on the value set.

How many cookies can a browser store per domain?

The HTTP specification suggests a minimum of 50 cookies per domain and 4096 bytes per cookie, but real browser limits vary. Chrome and Firefox allow around 180 cookies per domain. Generating a large batch of fake cookies lets you test whether your application degrades gracefully when approaching these limits, rather than discovering the problem in production.

What format are the expiry dates in the generated cookies?

Cookie expiry dates follow the RFC 1123 format required by the Set-Cookie specification: for example, Thu, 15 May 2026 10:30:00 GMT. This format must be exact — incorrect date formatting is a common source of cookies being silently ignored by browsers and HTTP clients, so using pre-formatted output removes that variable from your tests.

How do I add these cookies to a curl request for testing?

Copy a generated cookie string and pass it using curl's -H flag: curl -H 'Cookie: sessionId=abc123; userId=xyz456' https://yourapi.com/endpoint. For multiple cookies, combine them in a single Cookie header separated by semicolons, or use curl's --cookie flag with a file. The generated format is compatible with both approaches.