EchoBack.dev

Quick Start

curl https://example.echoback.dev

API

You can make any request toalmost any subdomain on echoback.dev (e.g. example.echoback.dev) and receive a response containing info about the request.

Subdomains

We support sending requests to multiple wildcard subdomains:

| Pattern | Example | | ------------------------- | ---------------------------------------------------------- | | *.echoback.dev/* | foo.echoback.dev | | *.dev.echoback.dev/* | foo.dev.echoback.dev | | *.test.echoback.dev/* | foo.test.echoback.dev | | *.vitest.echoback.dev/* | foo.vitest.echoback.dev |

Reserved Subdomains

The following subdomains are reserved and should not be used:

• docs.echoback.dev
• about.echoback.dev
• www.echoback.dev

Redacted Mode (Streamer Mode)

You may wish to redact sensitive information, such as IP addresses when using this service (e.g. for testing on a live stream or YouTube video). For these cases, you can use the following subdomains:

| Pattern | Example | | --------------------------- | ---------------------------------------------------------------------- | | redacted.echoback.dev/* | redacted.echoback.dev/foo | | redact.echoback.dev/* | redact.echoback.dev/foo | | r.echoback.dev/* | r.echoback.dev/foo | | *.redacted.echoback.dev/* | foo.redacted.echoback.dev/bar | | *.redact.echoback.dev/* | foo.redact.echoback.dev/bar | | *.r.echoback.dev/* | foo.r.echoback.dev/bar |

Redacted subdomains will redact the following information:

• Headers (set to "[REDACTED]"):

  • IP addresses (cf-connecting-ip, x-real-ip, x-forwarded-for, etc.)
  • cookie
  • authorization
  • *-key (suffix)
  • *-token (suffix)

• URL params (set to "REDACTED")

  • key
  • apikey
  • api_key
  • token
  • sk_* (secret key prefix)
  • rk_* (restricted secret key prefix)
  • ghu_* (GitHub token prefix)
  • ghp_* (GitHub token prefix)
  • gha_* (GitHub token prefix)

Response Format

Each response contains the following:

• Method
• URL
• Path
• Host
• Hostname
• Headers
• Body (when set on POST/PUT requests, otherwise returns null)

Example:

{
  "method": "GET",
  "url": "https://example.echoback.dev/foo",
  "path": "/foo",
  "host": "example.echoback.dev",
  "hostname": "example.echoback.dev",
  "headers": {
    "accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7",
    "accept-encoding": "gzip, br",
    "accept-language": "en-US,en;q=0.9",
    "cf-connecting-ip": "1.2.3.4",
    "cf-ipcountry": "US",
    "cf-ray": "9176984e3fb04776",
    "cf-visitor": "{\"scheme\":\"https\"}",
    "connection": "Keep-Alive",
    "cookie": "somedeliciouscookie",
    "host": "example.echoback.dev",
    "priority": "u=0, i",
    "sec-ch-ua": "\"Not A(Brand\";v=\"8\", \"Chromium\";v=\"132\", \"Microsoft Edge\";v=\"132\"",
    "sec-ch-ua-mobile": "?0",
    "sec-ch-ua-platform": "\"macOS\"",
    "sec-fetch-dest": "document",
    "sec-fetch-mode": "navigate",
    "sec-fetch-site": "none",
    "sec-fetch-user": "?1",
    "upgrade-insecure-requests": "1",
    "user-agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/132.0.0.0 Safari/537.36 Edg/132.0.0.0",
    "x-forwarded-proto": "https",
    "x-real-ip": "1.2.3.4"
  }
}

Redacted Example

{
  "method": "GET",
  "url": "https://example.echoback.dev/foo",
  "path": "/foo",
  "host": "example.echoback.dev",
  "hostname": "example.echoback.dev",
  "headers": {
    "accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7",
    "accept-encoding": "gzip, br",
    "accept-language": "en-US,en;q=0.9",
    "cf-connecting-ip": "[REDACTED]",
    "cf-ipcountry": "US",
    "cf-ray": "9176984e3fb04776",
    "cf-visitor": "{\"scheme\":\"https\"}",
    "connection": "Keep-Alive",
    "cookie": "[REDACTED]",
    "host": "example.echoback.dev",
    "priority": "u=0, i",
    "sec-ch-ua": "\"Not A(Brand\";v=\"8\", \"Chromium\";v=\"132\", \"Microsoft Edge\";v=\"132\"",
    "sec-ch-ua-mobile": "?0",
    "sec-ch-ua-platform": "\"macOS\"",
    "sec-fetch-dest": "document",
    "sec-fetch-mode": "navigate",
    "sec-fetch-site": "none",
    "sec-fetch-user": "?1",
    "upgrade-insecure-requests": "1",
    "user-agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/132.0.0.0 Safari/537.36 Edg/132.0.0.0",
    "x-forwarded-proto": "https",
    "x-real-ip": "[REDACTED]"
  }
}