writeFileAsBase64

Category: File Operations

Namespace: web.files.writeFileAsBase64

Description

Decodes a Base64 string and writes the raw bytes to a file on the local disk. Works with any file type — images, PDFs, audio, documents, or any other binary format. Parent directories are created automatically if they do not exist.

Use this API whenever you need to write binary data to a file. For plain text files, use writeTextFile() instead.

Syntax

const success = await web.files.writeFileAsBase64({
    filePath: string,
    data:     string
});

Parameters

• filePath (required) - Path where the file should be written (relative or absolute)
• data (required) - Base64-encoded binary content to write

Returns

Promise<boolean> - Returns true if the file was written successfully, false otherwise. Throws on error (invalid Base64, access denied, etc.)

Examples

Save a Base64 image to disk

// base64 could come from readFileAsBase64(), fetchToBase64(), a canvas export, etc.
const success = await web.files.writeFileAsBase64({
    filePath: 'C:\\Users\\Alice\\Pictures\\copy.jpg',
    data:     base64String
});

if (success) {
    console.log('Image saved successfully');
}

Export a canvas drawing as a PNG

const canvas  = document.getElementById('myCanvas');
// toDataURL returns "data:image/png;base64,iVBORw0K..." — strip the prefix first
const dataUrl = canvas.toDataURL('image/png');
const base64  = dataUrl.split(',')[1];

const success = await web.files.writeFileAsBase64({
    filePath: 'C:\\Exports\\drawing.png',
    data:     base64
});

Round-trip: read, process, write back

// Read the original
const base64 = await web.files.readFileAsBase64({
    filePath: 'C:\\Photos\\original.jpg'
});

// ... process the data in memory ...

// Write the result to a new path (parent folder created automatically)
const success = await web.files.writeFileAsBase64({
    filePath: 'C:\\Photos\\processed\\result.jpg',
    data:     base64
});

if (!success) {
    alert('Failed to save the processed file.');
}

Use Cases

• Save images received as Base64 (from canvas, API responses, etc.) to disk
• Write any binary file to disk from an in-memory Base64 string
• Round-trip binary files with readFileAsBase64()
• Export generated content (canvas drawings, processed images) as files

When to Use

Use writeFileAsBase64() when:

• You have binary data as a Base64 string that you want to save to disk
• You are writing images, PDFs, audio, or any other binary format

Use writeTextFile() when:

• The content is plain text (UTF-8), such as .txt, .json, .csv, .md

Use download() or downloadFromUrl() when:

• You want to save a remote file directly to disk without loading it into memory first

Notes

• Parent directories are created automatically (no need to create them first)
• Overwrites existing files without warning — check first with fileExists() if needed
• Relative paths are resolved from the application executable directory
• The data parameter must be a valid Base64 string — invalid input will throw an error
• Base64 encoding is approximately 33% larger than the original binary; the written file will be the correct original size