Base64 Decoder
Decode Base64 encoded text back to plain text instantly with automatic encoding detection.
What is Base64 Decoder?
The Base64 Decoder converts Base64 encoded strings back to their original plain text form. It validates the input for correct Base64 format (A-Z, a-z, 0-9, +, /, and = padding), handles UTF-8 decoding for international characters and emojis, and shows a clear error message if the input is malformed. All processing happens in the browser.
This tool takes a Base64 string, validates its format, and decodes it using the browser's atob function combined with UTF-8 handling. It supports the full Unicode range including accented characters, CJK text, and emojis. Invalid characters or incorrect padding trigger a descriptive error rather than silent data corruption.
Key Features
- Instant Base64 to text decoding
- Full Unicode and UTF-8 support
- Input validation with error messages
- Handles padding correctly
- Character count for input and output
- Copy decoded text to clipboard
- Quick example presets
- Runs in the browser with no uploads
Common Use Cases
Inspecting API response payloads
Decode Base64 encoded values found in API responses or server logs to see the original content.
Decoding JWT token segments
Paste a JWT header or payload segment (Base64URL encoded) to inspect the JSON claims.
Recovering encoded configuration values
Decode Base64 values stored in environment files or configuration YAML to verify their contents.
Debugging email MIME content
Decode Base64 encoded email body parts to read the original message text.
How to Use This Tool
Paste the Base64 string
Enter the encoded string in the input field. Padding (=) is optional.
Decode
Click Decode. The tool validates and converts the string.
Copy the result
Copy the decoded text for use in your application or analysis.
Pro Tips
- 1
Base64 strings only contain A-Z, a-z, 0-9, +, /, and = characters.
- 2
The tool handles Unicode output including emojis and accented characters.
- 3
For JWT tokens, decode each segment (header and payload) separately.
- 4
Base64 is not encryption. Anyone can decode it.
Frequently Asked Questions
Why does my Base64 string fail to decode?
Common reasons include invalid characters outside the Base64 alphabet, incorrect padding, or a truncated string. The tool shows a specific error message to help you fix the input.
What do the equal signs at the end mean?
Equal signs are padding characters. Base64 encodes data in 3-byte groups as 4 characters. Padding fills the output to a multiple of 4 when the input length is not divisible by 3.
Can I decode Base64 with Unicode output?
Yes. The tool uses UTF-8 decoding internally, so accented characters, CJK text, and emojis are correctly recovered from the Base64 input.
Is the decoding lossless?
Yes. Decoding Base64 produces the exact original text. No data is lost or modified during the process.
Is my input sent to a server?
No. All decoding happens in your browser using JavaScript. The text never leaves your device.