🔌 API Payload Encoder – Encode & Decode API Payloads Instantly
The API Payload Encoder is a browser-based developer utility for encoding and decoding API request and response payloads. Whether you need to Base64-encode a JSON body, convert form data to URL-encoded format, prepare a JWT-safe Base64URL payload, or generate a Basic Auth header, this tool handles every encoding scheme commonly used in REST, GraphQL, and SOAP APIs — all without sending your data to any server.
⚡ Supported Encoding Schemes
The tool supports seven encoding schemes covering the most common API transmission patterns:
| Scheme | Typical Use Case | Example Output |
|---|---|---|
| Base64 | Authorization headers, binary-safe transmission | eyJhcGlfa2V5Ijoi... |
| Base64URL | JWT payload segments (no padding) | eyJzdWIiOiIxMjM0... |
| URL Encode | Form POST bodies (application/x-www-form-urlencoded) | username=alice&pass=... |
| Query String | GET request parameters | ?search=api&page=2 |
| Basic Auth | HTTP Authorization header (username:password) | Authorization: Basic bXl... |
| Hex | Binary inspection, cryptography debugging | 7b226170695f6b6579... |
| Percent Encode | Individual URI components and query values | read%20write%20admin |
🔄 Bidirectional Encode & Decode
Toggle between Encode and Decode modes to reverse any supported transformation. Use the Swap & Flip button to instantly move the encoded output back into the input field with direction reversed — ideal for verifying that your encoding is correct and round-trips cleanly.
🧩 Quick Presets for Common Workflows
Five one-click presets cover the most frequent developer scenarios:
JSON → Base64
Encode a JSON object as standard Base64 for embedding in HTTP headers or storing in tokens.
JWT Payload (Base64URL)
Encode a JSON claims object using Base64URL with no padding — ready for the JWT payload segment.
Basic Auth Header
Enter username:password and get a ready-to-use Authorization: Basic ... header value.
Form Data & Query String
Convert a JSON object into URL-encoded form data for POST bodies, or into query strings for GET requests.
📋 HTTP Header & cURL Command Generation
After encoding, the tool automatically generates:
- HTTP Header Snippet — a ready-to-paste header line (e.g.,
Authorization: Basic ...orContent-Type: application/x-www-form-urlencoded) - cURL Command — a complete
curlcommand with the encoded payload embedded, ready to copy into your terminal or API testing workflow
📐 Byte Size & Overhead Indicator
Every encoding shows the original byte size, the encoded byte size, and the size overhead percentage. Base64 typically adds ~33% overhead; URL encoding varies by character composition. This helps you choose the most efficient encoding for latency-sensitive APIs.
🔒 Privacy & Security
All processing happens entirely in your browser using the native Web APIs (btoa, TextEncoder, encodeURIComponent). Your payload data, API keys, and credentials are never transmitted to any server. This makes the tool safe for use with production secrets.
⚠️ Security Note
Basic Auth and Base64 are not encryption — they are encoding schemes that anyone can reverse. Always transmit credentials over HTTPS and treat encoded credentials with the same care as plaintext passwords.
💡 Practical Examples
Encoding a JSON body as Base64 for an Authorization header:
Input: {"api_key":"sk-12345","scope":"read write"}
Output: eyJhcGlfa2V5Ijoic2stMTIzNDUiLCJzY29wZSI6InJlYWQgd3JpdGUifQ==Generating a Basic Auth header:
Input: myApiUser:s3cr3tP@ssw0rd
Output: Authorization: Basic bXlBcGlVc2VyOnMzY3IzdFBAc3N3MHJkConverting JSON to URL-encoded form data for a POST body:
Input: {"username":"alice","grant_type":"password"}
Output: username=alice&grant_type=password🛠️ Who Is This Tool For?
The API Payload Encoder is designed for backend developers, API integrators, QA engineers, and security researchers who regularly work with HTTP APIs. It replaces ad-hoc scripting with a focused, reliable, and always-available browser tool.