Illustrator
File › Scripts › Other Script… and pick the file. With a document open, the text lands in the middle of the active artboard; otherwise a new document is made.
InDesign
Window › Utilities › Scripts. Right-click the User folder › Reveal in Finder, drop the .jsx in, then double-click it in the panel. The frame auto-sizes to the text and the whole thing is one undo.
Photoshop
File › Scripts › Browse…. A new 72 ppi document opens with one editable type layer you can drag into your comp.
Base style
The base style is the one letters keep at 0% mix. It must be switched on in the pool: styles that are off are greyed out in the list, and switching off the base moves it to the nearest weight that is on.
Seed
Every random choice comes from the seed, so the same seed and settings always give the same result. Click Seed in the toolbar to type one, Enter to apply, Esc to cancel. Note a seed to get a layout back later.
Fonts
Fonts are matched by family and style name, then by PostScript name. Variable fonts use their named instances (Light, Bold…), so the app shows what the preview shows. Fonts the app can't find are listed and swapped for its default; the text stays editable.
Family share
Share of mix is each family's part of the letters that leave the base style. At first it follows the number of styles switched on. Drag one family and the others make room, keeping their proportions, so the total stays 100%. Styles keep their place in the light → heavy range.
Distribution
Ramp sets light → heavy from the start of the text to the end; Ramp per line restarts on every line. Alternate switches between the lighter and heavier half of the pool. Wave has a Period. Weight mix still decides how many letters leave the base style.
Even gaps
Where neighbouring letters come from different fonts, their sidebearings differ and the gaps look uneven. Even gaps adjusts the left letter's tracking so the gap moves halfway between the spacing of the two fonts it joins, instead of jumping from one to the other. It exports as tracking.
Match size
Different families at the same point size look different sizes. x-height or Cap height scales each letter's font so its lowercase x or capital H is as tall as in the base style (limited to 60–160%). It is written as the letter's point size, so it stays editable; leading follows the nominal size.
Letter align
Top, middle and bottom alignment are written as baseline shift values. If you change a letter or its font afterwards, export again to re-align.
Right panel
Selecting letters opens it with their font, size, shift and tracking at the top, then weight, align, rotation, fill and boxes. With nothing selected, the handle on the right edge opens the paragraph settings: hover info, the paragraph band, random letter boxes.
Boxes
Letter boxes follow each letter's ink, size and shift, and turn with it. A band runs under the selection, as tall as its tallest letter or stepping with each one; the paragraph band does the same for every line. Greys only. They export under the text as vector shapes: InDesign rectangles keep live corner options, Illustrator and Photoshop get the exact path.
Outline and rotation
Outline letters export as live text with no fill and a black stroke; rotation as character rotation, about the centre of the em box. Photoshop can do neither per letter inside one type layer, so those letters become their own type layers (outline as a layer-style stroke) and the main layer keeps a space of the same width.
Guides
Baseline, x-height, cap height and ascender of the base style at the set size. Tick Include guides to export them as plain lines on their own layer or group.