The Writable Files API: Simplifying local file access | Web | Google Developers

Today, if a user wants to edit a local file in a web app, the web app needs to ask the user to open the file. Then, after editing the file, the only way to save changes is by downloading the file to the Downloads folder, or having to replace the original file by navigating the directory structure to find the original folder and file. This user experience leaves a lot to be desired, and makes it hard to build web apps that access user files.

The writable files API is designed to increase interoperability of web applications with native applications, making it possible for users to choose files or directories that a web app can interact with on the native file system, and without having to use a native wrapper like Electron to ship your web app.

With the Writable Files API, you could create a simple, single file editor that opens a file, allows the user to edit it, and save the changes back to the same file. Or a multi-file editor like an IDE or CAD style application where the user opens a project containing multiple files, usually together in the same directory. And there are plenty more.

Read explainer

The primary entry point for this API is a file picker, which ensures that the user is always in full control over what files and directories a website has access to. Every access to a user selected file (either reading or writing) is done through an asynchronous API, allowing the browser to potentially include additional prompting and/or permission checks.

The Writable Files API provides web developers with significant access to user data and has potential to be abused. There are both privacy risks, for example websites getting access to private data they weren’t supposed to have access to, as well as security risks, for example websites able to modify executables, encrypt user data, and so forth. The Writable Files API must be designed in such a way as to limit how much damage a website can do, and make sure that the user understands what they’re giving the site access to.

Current status

Step Status
1. Create explainer Complete
2. Create initial draft of specification In progress
3. Gather feedback & iterate on design In progress
4. Origin trial Not started
5. Launch Not started


We need your help to design the Writable Files API in a way that will be useful in a way that is both secure and protects user privacy.

  • Have an idea for a use case or an idea where you'd use it?
  • Are there types of files or directories you don’t expect to have access to?
  • Do you plan to use this?
  • Like it, and want to show your support?

Share your thoughts on the Writable Files WICG Discourse discussion.

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