Base64 Decode & Encode

Decode base64 strings to text or JSON, or encode text to base64. Handles URL-safe base64 (- and _ characters), missing padding, and auto-formats JSON output.

Where developers use base64

JWT tokens

The header and payload sections of a JWT are base64url-encoded JSON. Decode the middle section to inspect claims: user ID, roles, expiry time, and any custom fields.

Basic Auth headers

HTTP Basic Authentication encodes credentials as base64(username:password). Decode an Authorization header to verify what credentials are being sent — useful when debugging auth failures.

Data URLs

Images embedded in CSS or HTML as data:image/png;base64,... contain base64-encoded binary data. Encoding text content the same way lets you embed small files inline.

API responses with encoded payloads

Some APIs (AWS SNS, GitHub webhooks) base64-encode the message body. Decode the payload field to see the actual event data.

Example

Decoding a JWT payload to inspect the claims

Input (base64url)

eyJ1c2VyIjoiYWxpY2UiLCJyb2xlIjoiYWRtaW4iLCJpYXQiOjE3MDUzMTIwMDB9

Output (decoded JSON)

{
  "user": "alice",
  "role": "admin",
  "iat": 1705312000
}

The decoded payload is valid JSON — auto-formatted for readability. The iat value is a Unix timestamp (seconds since epoch).

Frequently asked questions

What is base64 and why is it used?

Base64 encodes arbitrary bytes as printable ASCII characters using a 64-character alphabet (A-Z, a-z, 0-9, +, /). It's used whenever binary data needs to travel through a system that only handles text — email attachments, JSON API payloads, HTTP headers, and HTML data URLs all use base64 for this reason.

What is URL-safe base64?

Standard base64 uses + and / which have special meaning in URLs. URL-safe base64 (also called base64url) replaces + with - and / with _, and typically removes the = padding characters. JWTs always use URL-safe base64. Enable the URL-safe toggle when working with JWT payloads, URL parameters, or filenames.

How do I decode a JWT payload?

A JWT looks like xxxxx.yyyyy.zzzzz. The middle section (yyyyy) is the payload — base64url-encoded JSON. Copy just that section, paste it here with URL-safe mode enabled, and click Decode. You'll see the claims as formatted JSON.

I'm getting an 'Invalid character' error. What's wrong?

The input contains a character outside the base64 alphabet. Common causes: the string was URL-encoded (%3D instead of =), it contains whitespace or newlines, or it was truncated. Try enabling URL-safe mode if the string came from a JWT or URL parameter.

Can I encode a JSON object to base64?

Yes. Switch to Encode mode, paste your JSON (or any text), and click Encode. The output is the base64 string. Use URL-safe mode if the result will go in a URL or JWT.

Related Tools

TOOL

Validate JSONCheck if your JSON is valid, find the exact line where it breaks, and auto-fix common problems.

TOOL

Format JSONPaste compact JSON and make it readable, or paste pretty-printed JSON and compact it for production.

TOOL

JSON Path FinderPaste JSON, click any value, get the path expression. JSONPath, dot notation, or bracket notation — copy in one click.

{ }CSV

JSON → CSVPaste any JSON — flat, nested, or full of arrays — and get a clean CSV in seconds. No uploads, no account.

TOOL

Clean CSVFix encoding issues, inconsistent delimiters, ragged rows, trailing commas, and rogue quotes in broken CSV files.

TOOL

Flatten JSONCollapse any deeply nested JSON object into a single level of dot-notation keys.

All conversions run in your browser — nothing is uploaded.

Browse all 26 converters →