Base64 File Encoder / Decoder
100% Client-Side. Files never upload to any remote server.
About Base64 File Decoder
The Base64 to Binary File Decoder reconstructs original binary files (PDFs, ZIPs, MP3s, Images, Office Documents) from Base64 strings and Data URIs with automatic MIME-type sniffing and 1-click file download.
How to Use Base64 File Decoder
Step 1
Paste your Base64 string or Data URI into the editor.
Step 2
Review the auto-detected file type, MIME type, and decoded byte size.
Step 3
Inspect the live file preview if supported.
Step 4
Click "Download File".
Practical Use Cases for Base64 File Decoder
Decoding Base64 API Responses & Webhook Payloads
Convert Base64-encoded file attachments received from Stripe webhooks, SendGrid emails, and REST APIs back into downloadable binary files.
Inspecting Obfuscated Binary Data
Decode Base64 payloads found in logs, configuration files, and network traffic dumps to inspect their original file contents.
Input & Output Examples
Decoding Base64 to PDF Document
JVBERi0xLjQKJcTl8uXr... (Base64 string with PDF magic bytes `%PDF-1.4`)
Reconstructed document.pdf (124 KB | Valid PDF document ready for download)
Key Features & Performance
- ✓Auto-detects file format from magic bytes (PDF, ZIP, PNG, JPG, MP3, MP4, DOCX, XLSX).
- ✓Supports raw Base64, whitespace-separated chunks, and full `data:...;base64,` Data URIs.
- ✓In-browser live preview for images, audio, video, and text files.
- ✓100% Client-Side memory decoding via typed `Uint8Array` buffers.
- ✓1-Click Download reconstructed binary file.
Key Terminology & Definitions
Magic Byte Sniffing
Analyzing the first 4 to 8 bytes of decoded binary data (file signatures) to identify file type regardless of filename or extension.
`Uint8Array` Typed Array
A JavaScript array of 8-bit unsigned integers used to hold raw binary file buffers in memory before creating a downloadable Blob.