What is Base64 Encoding?
Base64 is an encoding scheme that converts binary data into 64 printable ASCII characters (A-Z, a-z, 0-9, +, /). It was developed to safely transmit binary data in text-only environments such as email attachments, web API communication, image-to-Base64 conversion (Data URIs), and JWT token payloads. It is defined by the RFC 4648 standard.
This free online Base64 converter encodes or decodes text, images, and files in real-time. It supports URL-Safe Base64, file upload, image preview, drag-and-drop, and conversion history (up to 10 entries). Full UTF-8 and Unicode support with all processing happening locally in your browser — your data never leaves your device.
Key Features
Real-time Encoding/Decoding
Enter text to instantly convert to Base64, or paste a Base64 string to restore the original text. Fully supports UTF-8 encoding.
URL-Safe Mode
URL-Safe mode replaces + with - and / with _, then removes trailing = padding. Check the alphabet and padding rules required by the receiving application.
File Upload & Image Preview
Upload files to automatically convert to Base64. Image files get a Data URI format preview.
Drag & Drop
Drag files into the input area for instant Base64 conversion. Fast and intuitive file processing.
How to Use
- Select Mode — Choose encode (text to Base64) or decode (Base64 to text) mode at the top.
- Enter Text or Upload File — Type or paste text to convert, or add files via the upload button or drag and drop.
- Set Options — URL-Safe replaces + with - and / with _, and removes trailing = padding. The line-break option inserts a break every 76 characters only when URL-Safe is off.
- Convert — Automatic conversion is on by default and updates the result about 0.3 seconds after input. The encode or decode button appears only when automatic conversion is off.
- Copy Result — Click the copy button to copy the conversion result to your clipboard.
Use Cases
API Development (Basic Auth)
In HTTP Basic Authentication, username:password is Base64 encoded and sent via the Authorization header. An essential encoding method for API testing.
Email Attachments
The MIME protocol uses Base64 to convert binary attachments into text format. It is the standard encoding method for email systems.
Data URI Image Embedding
Convert images to Base64 and embed them directly in HTML/CSS to display images without additional HTTP requests. Effective for small icons and logos.
Data Transfer & Storage
Use Base64 encoding when you need to include binary data in text-based formats like JSON or XML. Used in JWT tokens, configuration files, and more.
Base64 examples you can reproduce
Paste these exact inputs to check the results. Unless noted otherwise, use Encode with URL-Safe and line breaks off. Unicode text is converted through UTF-8 bytes, not its visible character count.
ASCII text and padding
- Input
Hello- Result
SGVsbG8=
Five input bytes produce eight characters including padding. The trailing = was not part of the original text.
Korean text in UTF-8
- Input
한글- Result
7ZWc6riA
These two characters occupy six UTF-8 bytes. No trailing padding is needed for this example.
An emoji in UTF-8
- Input
🙂- Result
8J+Zgg==
This emoji occupies four UTF-8 bytes. The standard Base64 result includes + and =.
The same emoji with URL-Safe on
- Input
🙂- Result
8J-Zgg
+ becomes - and trailing == is removed. In Decode mode, this result can be converted back to 🙂.
When a slash changes
- Input
???- Result
Pz8_
This is the result with URL-Safe on. Turn it off to get Pz8/. Both represent the same input.
Scope and limitations
- Base64 is not encryption. Do not use it to protect passwords or secret keys.
- File encoding is supported, but decoding and download are for UTF-8 text. This is not a binary-file recovery tool.
- File inputs larger than 15 MiB (15 × 1,024 × 1,024 bytes) are rejected. Smaller files can still be slow on memory-constrained devices.
- Standard Base64 without line breaks has 4 × ceil(n / 3) characters for n input bytes. Padding can make the percentage increase greater than 33% for short inputs.
FAQ
Is Base64 encoding encryption?
No, Base64 is encoding, not encryption. Anyone can easily decode it, so it's not suitable for protecting sensitive data. It should only be used for data format conversion purposes.
What is URL-Safe Base64?
Base64url replaces + with - and / with _. This tool's URL-Safe option also removes trailing = padding. Check the receiving API or format to see whether padding may be omitted.
Why does Base64 encoding increase size?
Base64 converts 6 bits into 8-bit ASCII characters, so the encoded data size increases by approximately 33%. (3 bytes → 4 characters)
Does decoding an image's Base64 download the original file?
This tool decodes bytes as UTF-8 text and downloads a .txt file. It does not reconstruct binary files such as images or PDFs. If your input is a full Data URI, remove the data:…;base64, prefix before decoding its payload as text.
Are my input and conversion history stored?
Conversion runs in your browser, but history is saved in localStorage. The last 10 records contain up to 2,000 characters each of input and output, the mode, and a timestamp. Records may be saved after pausing in automatic text mode or when converting, copying, or downloading. Open Conversion History and choose Clear All. Clearing the input alone does not delete history.
Why can valid Base64 produce unreadable text?
Base64 represents bytes without specifying their character encoding. This tool reads decoded bytes as UTF-8. Another encoding or binary data such as an image may produce replacement characters (�). Check the UTF-8 validity badge; having output does not prove that the original data was correctly restored.
Privacy Notice
Conversion runs in your browser; the converter code does not upload your input text or files to a conversion server. However, the last 10 conversion records are saved in this browser's localStorage, including up to 2,000 characters each of input and output, the mode, and a timestamp. Copying or downloading a file conversion can also save part of its result. Delete records using Conversion History → Clear All. Avoid sensitive input on shared devices: closing the tab or clearing only the input does not necessarily remove history. See the site's privacy policy for separate advertising and usage-analytics information.
Comments & questions