DeveloperKit

Base64 to JSON Decoder

Decode Base64 into validated, readable JSON instantly. Free, private, and 100% in your browser.

Input Base64

JSON Output

JSON output will appear here.

Decode Base64 to JSON Online

JSON is often transported as Base64: in JWT tokens, Kubernetes Secrets, webhook payloads, message queues, and API fields. This decoder turns that Base64 back into JSON, validates it, and formats it so you can read it right away.

Features

  • Decode and format

    Base64 is decoded and the JSON is validated and pretty-printed in one step.

  • Forgiving input

    Accepts standard Base64 and base64url, line breaks, missing = padding, and data:...;base64, prefixes.

  • Precise errors

    Invalid Base64 characters are reported with their line and column, and invalid JSON with its exact location.

  • Full UTF-8 support

    Decoded bytes are read as UTF-8, so accented letters and emoji come back correctly.

  • Raw output option

    Choose As decoded to see the exact decoded text, even if it is not valid JSON.

  • Private by design

    Decoding runs entirely in your browser. Your data is never uploaded.

Base64 to JSON Example

Base64 input
eyJ1c2VyIjoiYWRhIiwicm9sZXMiOlsiYWRtaW4iLCJlZGl0b3IiXSwiYWN0aXZlIjp0cnVlfQ==
JSON output
{
  "user": "ada",
  "roles": [
    "admin",
    "editor"
  ],
  "active": true
}

How to Decode Base64 to JSON

  1. Paste your Base64 string into the input editor, or upload a text file.
  2. The JSON output appears instantly, validated and formatted.
  3. Choose pretty, minified, or As decoded output.
  4. Copy the JSON or download it as a .json file.

Frequently Asked Questions

How do I decode a JWT payload?

A JWT has three parts separated by dots. Paste the middle part (the payload) into the input. It is base64url-encoded JSON, which this tool decodes automatically. Note that decoding a JWT does not verify its signature.

What if the decoded text is not JSON?

You will see an error with the line and column of the problem in the decoded text. Switch the output to As decoded to see the raw text instead.

Why does it say the data is not valid UTF-8 text?

The Base64 data most likely contains a binary file, such as an image, PDF, or ZIP archive, rather than text. Those cannot be shown as JSON.

Do I need to remove line breaks or padding?

No. Whitespace and line breaks are ignored, and missing = padding is accepted, so you can paste Base64 exactly as you found it.

Is my data uploaded anywhere?

No. Decoding runs entirely in your browser. Your data never leaves your device.

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