ExifTool (13.11) powered by WebAssembly to extract and write metadata from/to files in browsers and Node.js environments using zeroperl.
npm install @uswriting/exiftool
This package provides a WebAssembly-based implementation of ExifTool that works in both browser and Node.js environments. It leverages zeroperl to execute ExifTool without requiring any native binaries or system dependencies.
import { parseMetadata } from '@uswriting/exiftool';
// Browser usage with File API
document.querySelector('input[type="file"]').addEventListener('change', async (event) => {
const file = event.target.files[0];
const result = await parseMetadata(file);
if (result.success) {
console.log(result.data);
} else {
console.error('Error:', result.error);
}
});import { parseMetadata } from '@uswriting/exiftool';
const result = await parseMetadata(file, {
args: ['-Author', '-CreateDate', '-Make', '-Model']
});
if (result.success) {
console.log(result.data);
}import { parseMetadata } from '@uswriting/exiftool';
const result = await parseMetadata(file, {
args: ['-json', '-n'],
transform: (data) => JSON.parse(data)
});
if (result.success) {
// Typed access to properties
console.log(result.data); // { ... }
}This example demonstrates writing basic XMP tags to a selected file using a string array for tags.
import { writeMetadata, ExifToolWriteOptions } from '@uswriting/exiftool';
// 'selectedFile' is a File object obtained from user input.
if (selectedFile) {
const tagsToWrite: string[] = [
"-XMP-dc:Description=My test image",
"-XMP-photoshop:Credit=Photographer Name",
"-XMP-dc:Subject=Nature, Landscape"
];
const options: ExifToolWriteOptions = {
tags: tagsToWrite
// For more advanced options like 'configFile' or 'extraArgs',
// refer to the API Reference for ExifToolWriteOptions.
};
const result = await writeMetadata(selectedFile, options);
if (result.success) {
// Modified file contents
console.log(result.data); // { ... }
}
}- In browser environments, pass the
Fileobject directly from file inputs. Do not convert it to an ArrayBuffer or Uint8Array. - The
writeMetadatafunction returns a newUint8Arraycontaining the modified file data. The original file object is not changed. - This package uses asynchronous web APIs for file processing which allows handling files over 2GB without loading them entirely into memory.
- ExifTool is executed entirely within the browser or Node.js environment - no server requests are made for metadata extraction.
async function parseMetadata<TReturn = string>(
file: Binaryfile | File,
options: ExifToolOptions<TReturn> = {}
): Promise<ExifToolOutput<TReturn>>file: Either a browserFileobject or aBinaryfileobject withnameanddataproperties.options: Configuration options for the metadata extraction.
interface ExifToolOptions<TReturn> {
// Additional command-line arguments to pass to ExifTool
args?: string[];
// Custom fetch implementation for loading the WASM module
fetch?: (...args: any[]) => Promise<Response>;
// Transform the raw ExifTool output into a different format
transform?: (data: string) => TReturn;
}Returns a Promise that resolves to an ExifToolOutput object:
type ExifToolOutput<TOutput> =
| {
success: true;
data: TOutput;
error: string;
exitCode: 0;
}
| {
success: false;
data: undefined;
error: string;
exitCode: number | undefined;
};async function writeMetadata(
file: Binaryfile | File,
options: ExifToolWriteOptions
): Promise<ExifToolWriteResult>file: Either a browserFileobject or aBinaryfileobject ({ name: string, data: Uint8Array | Blob }) representing the file to modify.options: Configuration options for writing metadata.
// Defines possible values for a tag when using TagsObject.
type TagValue = string | number | boolean | (string | number | boolean)[];
// Represents tags as a JavaScript object for writing metadata.
type TagsObject = Record<string, TagValue>;
interface ExifToolWriteOptions {
// Tags to write. Can be an array of ExifTool arguments (e.g., `["-Comment=Test"]`)
// or a `TagsObject` (e.g., `{ "Comment": "Test", "IPTC:Keywords": ["one", "two"] }`).
tags: string[] | TagsObject;
// Optional: Custom ExifTool config file for defining custom tags.
// Provide as { name: string, data: Uint8Array }.
configFile?: {
name: string;
data: Uint8Array;
};
// Custom fetch implementation for loading the WASM module.
fetch?: (...args: any[]) => Promise<Response>;
// Additional command-line arguments for ExifTool (e.g., `-m` for ignore minor errors).
// Avoid input/output filenames or tag assignments here.
extraArgs?: string[];
}Returns a Promise that resolves to an ExifToolWriteResult object:
type ExifToolWriteResult =
| {
success: true;
data: Uint8Array;
warnings: string;
exitCode: 0;
}
| {
success: false;
data: undefined;
error: string;
exitCode: number | undefined;
};Apache License, Version 2.0