How do I decode a Base64 string?

Simply paste your Base64-encoded string into our decoder and click 'Decode'. The tool will instantly convert the Base64 text back to its original form. Our decoder handles standard Base64, URL-safe Base64, and automatically detects the encoding format.

What is a JWT (JSON Web Token)?

A JWT (JSON Web Token) is a compact, URL-safe token format used for securely transmitting information between parties. It consists of three parts: a header (specifying the algorithm), a payload (containing claims like user ID, expiration), and a signature (for verification). JWTs are commonly used for authentication and authorization in web applications.

How do I decode a JWT token?

Paste your JWT token into our decoder and select the 'JWT' tab. The tool will parse the token and display the header, payload, and signature separately. You'll see all claims including issuer (iss), subject (sub), expiration (exp), and any custom claims. The tool also shows if the token has expired.

What are common JWT claims and what do they mean?

Common JWT claims include: 'iss' (issuer - who created the token), 'sub' (subject - typically user ID), 'aud' (audience - intended recipient), 'exp' (expiration time), 'iat' (issued at - creation time), 'nbf' (not before - when token becomes valid), and 'jti' (JWT ID - unique identifier). Custom claims can include user roles, permissions, and application-specific data.

Is it safe to decode JWT tokens online?

Our JWT decoder runs entirely in your browser - no data is sent to any server. The token never leaves your device, making it completely safe for decoding sensitive tokens. However, remember that JWT payloads are only Base64-encoded (not encrypted), so never put secrets in JWT claims.

What's the difference between Base64 and Base64URL encoding?

Standard Base64 uses '+' and '/' characters which have special meanings in URLs. Base64URL encoding replaces '+' with '-' and '/' with '_', making it safe for use in URLs and filenames. JWTs use Base64URL encoding. Our tool handles both formats automatically.

How can I tell if a JWT has expired?

Our JWT decoder automatically checks the 'exp' (expiration) claim and displays whether the token is still valid or has expired. It shows the exact expiration date/time and calculates how long until expiry or how long ago it expired. This helps you debug authentication issues quickly.

decoder

Base64 Encoder/Decoder & JWT Token Decoder

Encode and decode Base64 strings instantly. Parse JWT tokens to inspect headers, claims, signatures, and check expiration times. All processing happens in your browser - your data never leaves your device.

Mode:

Base64 Input

Common JWT Claims

iss - Issuer (who created the token)

sub - Subject (user ID or identifier)

aud - Audience (intended recipient)

exp - Expiration time (Unix timestamp)

iat - Issued at (creation timestamp)

nbf - Not before (token validity start)

How to Use This Tool

Choose Mode

Select Base64 encode/decode or JWT decode mode using the tabs above the input area

Enter Your Data

Paste your Base64 string, plain text, or JWT token into the input field

Get Results

View the decoded/encoded output instantly. For JWTs, explore header, payload, and signature details

Base64 vs JWT: Understanding the Difference

Base64 Encoding

Base64 is a simple encoding scheme that converts binary data to ASCII text. It's not encryption - anyone can decode it. Use Base64 for:

Embedding images in HTML/CSS (data URIs)
Sending binary data in JSON/XML
Email attachments (MIME encoding)
Storing binary data in text databases

JSON Web Tokens (JWT)

JWTs are structured tokens with a signature for verification. They use Base64URL encoding internally. Use JWTs for:

Authentication (login tokens)
Authorization (API access)
Information exchange between services
Stateless session management

Frequently Asked Questions

Base64 is a binary-to-text encoding scheme that converts binary data into ASCII characters. It's commonly used to embed images in HTML/CSS, send binary data in JSON/XML, encode email attachments, and transmit data through text-only systems. Base64 increases data size by about 33% but ensures safe transmission through any text-based protocol.

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