Add it to your own website

If you run a website, you can give every visitor the same −/+ text-size control without them installing anything. Add one line to your pages, anywhere in <head> or before </body>:

<script src="https://narve.github.io/text-size-adjuster/embed/text-size-adjuster.js"></script>

That's all. The control appears in the bottom-right corner, scales your page's text while keeping headings bigger than body text, and doesn't change your layout's width. See it on a demo page.

Options

Set them as attributes on the script tag:

<script
  src="https://narve.github.io/text-size-adjuster/embed/text-size-adjuster.js"
  data-position="top-left"
  data-show="on-zoom"
></script>

…or as parameters on the script's address, if attributes are awkward in your setup:

<script src="https://narve.github.io/text-size-adjuster/embed/text-size-adjuster.js?position=tl&show=on-zoom"></script>

position also accepts the long forms top-left, top-right, bottom-left and bottom-right. on-zoom keeps the control hidden until the visitor zooms in (pinch, or browser zoom). If an option is set both ways, the attribute wins. Unknown values are ignored.

Good to know:

• For a production site, download that file and serve it from your own server instead of linking to this documentation site — that way it can't change or disappear underneath you.
• The copy on this site is replaced whenever a new version is published, so an integrity attribute (Subresource Integrity) on a script tag pointing at it would stop working at the next update. With your own copy you can add one.
• The chosen size is not remembered between page loads; each visit starts at normal size. (The browser extension is the version that remembers a size per site.)
• A visitor who hides the control with × gets it back when the page is loaded again.
• This only works on sites you control. To use the control on other people's sites, install the Firefox add-on instead.