File to Base64 Converter
Convert any file to Base64 instantly — PDF, images, ZIP, audio, video
File Input
Drop any file here or click to upload
PDF, Word, Excel, ZIP, images, audio, video — any file type up to 10MB
Base64 Output
What is File to Base64 Conversion?
Base64 encoding converts binary file data into a plain-text string. This lets you embed any file — Word documents, ZIP archives, audio, or images — directly inside JSON, XML, HTML, or API request bodies without needing a separate file upload endpoint. The RFC 4648 standard defines the encoding algorithm used by this tool.
Modern APIs such as the browser FileReader API produce data URIs in the format data:;base64, — the exact format this tool outputs by default.
All conversion happens in your browser using the native FileReader API and btoa(). Your files never leave your device.
How to Use the File to Base64 Converter
Follow these steps to convert files to Base64. Each step uses the actual buttons and panels on this page.
Upload a File
Click Upload File or drag and drop onto the left File Input panel. Supports PDF, Word, images, ZIP, and any file type up to 10MB. Example: subscriber bill PDF, carrier invoice, or contract.
Choose Output Format
Select Data URI for a full data:mime;base64,... string (HTML/CSS ready), or Raw Base64 if your API expects just the encoded data.
Copy or Download
Click Copy to copy to clipboard, or Download to save as .txt. Use Clear to start fresh. All conversion runs in your browser.
When You'd Actually Use This
API File Uploads via JSON
Many REST APIs — including Twilio MMS and document APIs — accept files as Base64 strings in JSON bodies, bypassing the need for multipart form data.
Kubernetes & CI/CD Secrets
Store TLS certificates, SSH keys, or config files as Base64 in Kubernetes Secrets or GitHub Actions Encrypted Secrets.
Embedding Files in HTML/CSS
Embed fonts, icons, or small assets directly in data URIs inside CSS or HTML to reduce HTTP requests and create self-contained documents.
Email Attachments (SMTP)
Build MIME-encoded emails (RFC 2045) manually or through SMTP libraries. Attachments must be Base64-encoded before being included in the email body.
Common Questions
What file types are supported?
All file types are supported. The tool uses the FileReader API to read raw binary data and encode it, regardless of file format.
Why is the Base64 string larger than my file?
Base64 encoding increases size by approximately 33% — every 3 bytes becomes 4 ASCII characters. This is a fundamental property of Base64, not a bug.
Which output format should I use?
"Data URI" is best for HTML , , or CSS url(). "Raw Base64" is best for API request bodies, JSON fields, or any context that handles the MIME type separately.
Can I convert the Base64 back to the original file?
Yes! Use our Base64 to File tool — paste the Base64 string, specify the file type, and download the original file.
Is there a file size limit?
The tool supports files up to 10MB. Larger files may cause browser performance issues depending on available memory.
Is my file data private?
Yes. All conversion happens in your browser using the native FileReader API. Your files never leave your device or connect to our servers.
Related Base64 Tools
Complete your Base64 workflow: