Scribble makes handing off a mockup to developers easier by annotating text layers in a PSD with font information.

It was created out of necessity for developers to have the information they needed to implement a design. Scribble adds a new annotation layer group and marks up your document with a legend of unique fonts and corresponding markers beside your layers. This is done non-destructively so you still have a useable PSD to work with.

It’s written in JSX, Adobe’s JavaScript subset that gives you access to the Photoshop DOM (Document Object Model, like on a webpage). Similar to the DOM in a web browser, the Photoshop DOM can be very slow to manipulate. Because of this, a large part of the script was hand-optimized to avoid touching the DOM, instead working with Photoshop’s Action* functions that are much faster.