Free Base64 Decoder — Convert Base64 to Text, Files & Binary Data Online

What Is Base64 Decoding?

Base64 decoding is the process of converting a Base64-encoded string back into its original form — whether that's plain text, binary data, an image, or any other file type. It reverses the Base64 encoding process, transforming the text-safe representation back to usable data.

Developers, system administrators, and security professionals frequently need to decode Base64 strings when debugging API responses, reading email headers, inspecting authentication tokens, or extracting embedded content.

Why You Need a Base64 Decoder

• Debug API Responses: Many APIs return data in Base64 format — decode it to inspect the actual content.
• Read Email Headers: Email subjects and content encoded in Base64 (MIME) need decoding to be human-readable.
• Inspect JWT Tokens: JSON Web Tokens use Base64url encoding for their header and payload sections.
• Extract Embedded Data: Data URIs in HTML/CSS contain Base64-encoded content that you may need to extract.
• Security Analysis: Malware and phishing attempts often use Base64 encoding to obfuscate payloads.

How to Decode Base64

1. Paste the Base64-encoded string into the input field.
2. Click the Decode button.
3. View and copy the decoded output — the original text or data will be displayed.

Understanding Base64 Character Set

Valid Base64 strings contain only these characters: A-Z, a-z, 0-9, +, /, and the padding character =. The URL-safe variant uses - instead of + and _ instead of /. If your input contains other characters, it's not valid Base64.

Common Use Cases

• Decode API authentication headers — Read HTTP Basic Auth credentials from Base64
• Inspect JWT token contents — Decode the header and payload sections of JSON Web Tokens
• Read encoded email content — Decode MIME-encoded email subjects and body text
• Extract data from URIs — Pull images or files from Base64 data URIs
• Reverse-engineer obfuscated data — Decode Base64 strings found in scripts, configs, or logs

Best Practices

• Validate before decoding — Ensure your string is valid Base64 (only contains allowed characters) to avoid errors.
• Check encoding variant — Standard Base64 uses +/ while URL-safe Base64 uses -_. Make sure you're using the right decoder.
• Handle padding correctly — Some implementations omit trailing = padding. If decoding fails, try adding padding characters.
• Be cautious with unknown data — Decoded Base64 could contain malicious content. Don't execute decoded data without inspection.

Related Tools

• Base64 Encoder — Convert text and data to Base64 format
• Base64 to Image — Decode Base64 strings into viewable images
• Image to Base64 — Convert images to Base64-encoded strings
• URL Decoder — Decode percent-encoded URL strings
• JSON Validator & Beautifier — Validate and format decoded JSON data

Frequently Asked Questions

Can Base64 decoding recover encrypted data?

No. Base64 decoding only reverses Base64 encoding. If data was encrypted before being Base64-encoded, decoding it will give you the encrypted (still unreadable) data. You'll need the correct decryption key and algorithm to access the original content.

Why does my decoded Base64 output look like garbage characters?

This usually means the original data was binary (an image, PDF, or compressed file) rather than text. Binary data displayed as text appears as garbled characters. Try using a specialized tool like Base64 to Image if you suspect the data is an image.

What's the difference between Base64 and Base64url encoding?

Standard Base64 uses + and / characters, which have special meaning in URLs. Base64url replaces these with - and _ to make the encoded string URL-safe. JWT tokens and many modern APIs use Base64url encoding.

Is there a size limit for Base64 decoding?

Our online tool handles strings up to several megabytes. For very large files, consider using command-line tools like base64 -d on Linux/macOS or programming libraries in your preferred language.