Base64 File & Text Encoder / Decoder
What It Is
This tool encodes text or files to Base64 strings and decodes Base64 strings back to their original binary files or plain text, entirely in the browser. Developers use it to convert images to Data URIs, inspect binary file contents, test API payloads, and restore Base64-encoded files back to PNG, JPEG, PDF, ZIP, MP3, and document formats.
How File Decoding Works
When decoding a Base64 string back to a file, the tool reads the binary byte sequence and detects magic byte signatures (e.g., 89 50 4E 47 for PNG, FF D8 FF for JPEG, 25 50 44 46 for PDF). It creates a client-side Blob URL allowing instant previewing and downloading of the restored file without server intervention.
Frequently Asked Questions
Q:What is Base64 encoding used for?
Base64 encodes binary data into ASCII characters. It is commonly used for embedding images in CSS/HTML, transmitting binary files via HTTP, and encoding JWT tokens. The encoding increases data size by approximately 33%, making it inefficient for large files.
Q:Is my file data secure when encoding or decoding?
Yes. All encoding and decoding happen 100% client-side in your browser. No files or Base64 strings are uploaded to any server, and no data leaves your device.
Q:How does Base64 file decoding work?
Paste any Base64 string or Data URL (e.g. data:image/png;base64,...). The tool automatically parses the binary header and magic bytes to detect the file type (PNG, JPG, PDF, ZIP, MP3, etc.), renders an interactive preview, and lets you download the exact decoded file with 1 click.
Q:What is the difference between Base64 and Base64URL?
Standard Base64 uses + and / as the 63rd and 64th characters, which are not URL-safe. Base64URL replaces them with - and _ respectively, and omits padding (=). Enable URL-SAFE mode to decode URL-encoded Base64 strings.
Q:Why does Base64 increase the data size by about 33%?
Base64 maps every 3 bytes (24 bits) of input into 4 ASCII characters (6 bits each = 24 bits). For every 3 input bytes, you get 4 output characters. The overhead ratio is 4/3 = 1.33, hence ~33% larger.