To download a file with fetch() , you follow a three-step process: Request the file from the server.
How to Download a File Using JavaScript Fetch Downloading files using the is a modern and versatile approach that provides more control than traditional links. Unlike simple tags, using fetch() allows you to add custom headers for authentication (like Bearer tokens), track download progress, and handle errors before a file ever reaches the user's disk. The Core Workflow javascript fetch download file
This is the standard method for downloading small-to-medium files (e.g., PDFs, images, or JSON). javascript To download a file with fetch() , you
Create a temporary URL and programmatically click a hidden anchor element to save it. 1. Basic File Download Example The Core Workflow This is the standard method
Transform the response into a Blob object (Binary Large Object).
async function downloadFile(url, fileName) { try { const response = await fetch(url, { method: 'GET', headers: { 'Authorization': 'Bearer YOUR_TOKEN_HERE' // Optional: Custom headers } }); if (!response.ok) throw new Error(`HTTP error! Status: ${response.status}`); const blob = await response.blob(); const downloadUrl = window.URL.createObjectURL(blob); const a = document.createElement('a'); a.href = downloadUrl; a.download = fileName; // Suggests a filename to the browser document.body.appendChild(a); a.click(); // Cleanup to prevent memory leaks window.URL.revokeObjectURL(downloadUrl); document.body.removeChild(a); } catch (error) { console.error('Download failed:', error); } } Use code with caution.
Standard fetch() does not have a built-in "progress" event like the older XMLHttpRequest . To track progress, you must use the Streams API to read the response body in chunks. Get the total file size from the Content-Length header. Use response.body.getReader() to read incoming byte chunks. Update your UI (like a progress bar) as each chunk arrives. Fetch API Download Progress Indicator? - Stack Overflow