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Base64 Encoder/Decoder

Encode and decode Base64 strings online free

Text to Encode

Drag & drop a file or use Upload File button

About

Encodes and decodes Base64 data with automatic input detection (plain text vs. Base64 string). Supports standard Base64, base64url (URL-safe), data URI generation for images/media, and four character encodings (UTF-8, ASCII, UTF-16LE, UTF-16BE). Includes file drag-and-drop, batch mode for processing multiple items, and real-time character count comparison.

Base64 encoding is essential for embedding binary data in text-based formats like JSON, HTML, CSS, and URLs. A reliable multi-format tool handles edge cases like URL safety, encoding variants, and batch operations without switching between utilities.

Who should use this tool?

Web developers, API designers, software engineers working with binary data transmission, and anyone embedding images or files in text-based formats.

Common use cases

Encode an image to a data URI for inline embedding in CSS or HTML
Decode a JWT token's payload (base64url-encoded) for inspection
Convert a binary file to Base64 for transmission in a JSON API payload
Batch-encode multiple small files for bundling into a single configuration file
Use base64url encoding to generate URL-safe tokens without padding
Verify whether a given string is valid Base64 using auto-detect

How to Use

Paste your input text or drag-and-drop a file — auto-detects if input is plain text (to encode) or Base64 (to decode)

Select character encoding: UTF-8 (default), ASCII, UTF-16LE, or UTF-16BE

Choose output format: Standard Base64, Base64 URL, or Data URI (prepends correct MIME type)

Click 'Encode' or 'Decode' — result appears with size comparison showing input vs. output byte count

For batch mode, switch to 'Batch' tab and enter multiple values (one per line) — each processed independently

Copy individual results or entire batch output, or use 'Download' to save as a text file

Examples

Input: 'Hello World' | Encode | UTF-8 | Standard => Output: 'SGVsbG8gV29ybGQ=' (standard Base64 with padding)

Input: 'SGVsbG8gV29ybGQ' | Decode | Auto-detect => Output: 'Hello World' (decoded without padding)

Best Practices

Use base64url when encoding data for URLs or filenames to avoid '+/=' characters that need percent-encoding
For large files (10+ MB), consider chunked encoding to avoid memory issues
When embedding images in CSS, use data URI output format — prepends correct 'data:image/...;base64,' prefix
Verify output size: Base64 inflates data by ~33% — ensure your transport medium can handle the overhead
Use UTF-16LE or UTF-16BE only when targeting legacy systems requiring those encodings

Common Mistakes

Using standard Base64 in URLs without switching to base64url — '+' and '/' break URL parsing
Decoding a Base64 string without verifying validity — garbage input produces garbage output
Forgetting Base64 is encoding, not encryption — never use it to protect sensitive data
Selecting wrong character encoding when encoding, causing garbled decoded output on the receiving end
Dragging very large files without monitoring output size — some browsers may freeze or crash

FAQ

What is the difference between Base64 and base64url?

Base64 uses '+/=' which are not URL-safe. base64url uses '-_' and strips padding.

Can I encode images with this tool?

Yes, drag-and-drop any image file. The tool encodes it and optionally adds data URI header.

How do I process multiple files at once?

Switch to 'Batch' mode and paste multiple values or use multi-file upload.

Does the tool support streaming for large files?

Files are processed in memory. For >50 MB, use a command-line tool.

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Learning Resources

Dive deeper with our comprehensive guides and tutorials.

Base64 Encoder/Decoder - Beginner's Guide

5 min read

Base64 Encoder/Decoder Advanced Techniques

8 min read

About

Who should use this tool?

Web developers, API designers, software engineers working with binary data transmission, and anyone embedding images or files in text-based formats.

Common use cases

Encode an image to a data URI for inline embedding in CSS or HTML
Decode a JWT token's payload (base64url-encoded) for inspection
Convert a binary file to Base64 for transmission in a JSON API payload
Batch-encode multiple small files for bundling into a single configuration file
Use base64url encoding to generate URL-safe tokens without padding
Verify whether a given string is valid Base64 using auto-detect

How to Use

Paste your input text or drag-and-drop a file — auto-detects if input is plain text (to encode) or Base64 (to decode)

Select character encoding: UTF-8 (default), ASCII, UTF-16LE, or UTF-16BE

Choose output format: Standard Base64, Base64 URL, or Data URI (prepends correct MIME type)

Click 'Encode' or 'Decode' — result appears with size comparison showing input vs. output byte count

For batch mode, switch to 'Batch' tab and enter multiple values (one per line) — each processed independently

Copy individual results or entire batch output, or use 'Download' to save as a text file

Best Practices

Use base64url when encoding data for URLs or filenames to avoid '+/=' characters that need percent-encoding

For large files (10+ MB), consider chunked encoding to avoid memory issues

When embedding images in CSS, use data URI output format — prepends correct 'data:image/...;base64,' prefix

Verify output size: Base64 inflates data by ~33% — ensure your transport medium can handle the overhead

Use UTF-16LE or UTF-16BE only when targeting legacy systems requiring those encodings

Common Mistakes

Using standard Base64 in URLs without switching to base64url — '+' and '/' break URL parsing

Decoding a Base64 string without verifying validity — garbage input produces garbage output

Forgetting Base64 is encoding, not encryption — never use it to protect sensitive data

Selecting wrong character encoding when encoding, causing garbled decoded output on the receiving end

Dragging very large files without monitoring output size — some browsers may freeze or crash

FAQ

What is the difference between Base64 and base64url?

Base64 uses '+/=' which are not URL-safe. base64url uses '-_' and strips padding.

Can I encode images with this tool?

Yes, drag-and-drop any image file. The tool encodes it and optionally adds data URI header.

How do I process multiple files at once?

Switch to 'Batch' mode and paste multiple values or use multi-file upload.

Does the tool support streaming for large files?

Files are processed in memory. For >50 MB, use a command-line tool.

Base64 Encoder/Decoder

About

Who should use this tool?

Common use cases

How to Use

Examples

Best Practices

Common Mistakes

FAQ

Related Tools

Same Category — Encoders

URL Encoder/Decoder

Base64 Image Converter

String Escape/Unescape

HTML Entity Encoder/Decoder

Popular Tools

JSON Formatter

JWT Decoder

SQL Formatter

Learning Resources

Share

Base64 Encoder/Decoder

About

Who should use this tool?

Common use cases

How to Use

Examples

Best Practices

Common Mistakes

FAQ

Related Tools

Same Category — Encoders

URL Encoder/Decoder

Base64 Image Converter

String Escape/Unescape

HTML Entity Encoder/Decoder

Popular Tools

JSON Formatter

JWT Decoder

SQL Formatter

Learning Resources

Share