Text Size

1. Download the zip above and unzip it. You get a folder called mes-text-size. Keep it somewhere permanent (Documents is fine): the browser reads the extension from that folder.
2. Open the extensions page (click an address to copy it, then paste it into the address bar: browsers do not let web pages link to these): chrome://extensions in Chrome, brave://extensions in Brave, edge://extensions in Edge.
3. Turn on Developer mode (a switch at the top right, or on the left in Edge).
4. Click Load unpacked and choose the unzipped mes-text-size folder.
5. Click the puzzle-piece icon in the toolbar and pin MES Text Size.

Chrome may show a "disable developer mode extensions" notice when it starts: choose Cancel / Keep. Brave and Edge usually do not. Until the extension is listed in the Chrome Web Store, updates are manual: download the new zip, replace the folder and press the reload arrow on the extensions page. Firefox is not supported yet.

• Click the toolbar icon and press A+ or A−, drag the slider or pick a preset. Only that tab changes: other tabs, even of the same site, keep their size.
• Alt+Shift+Up / Down change the size, Alt+Shift+0 goes back to normal. Change the shortcuts at chrome://extensions/shortcuts.
• This tab, this site or all sites. The popup's Change the size for menu picks where a change goes: this tab only (the default: it stays for reloads, back / forward and links within the same site in that tab, and is forgotten when the tab goes to another site or closes), this site (all tabs) (remembered, every open page of that site follows at once) or all sites (every site without a size of its own). A tab's own size wins over the site's; Use the site's size in this tab removes it.
• In the settings: the step (5 to 25%), the default for Change the size for, the all-sites size, and the list of sites that have their own size.
• Updating from 1.0: version 1.0 remembered every change for the whole site. Those site sizes are kept (remove any you no longer want in the settings), and new changes now go to the tab you are in unless you pick this site or all sites. Reload pages that were open while you updated.

Every piece of text on the page gets its own size (and line height) equal to what it had times your percentage. The original values are remembered, so any size, and 100%, is exact, and text that appears later (menus, comments, infinite scroll, lists a page re-draws) is scaled before the browser shows it, so it does not flash at the old size. Sizes that depend on each other (em, percentages, inherited text) are never scaled twice.

Because only text grows, a page built with fixed-height boxes can overflow or overlap at large sizes; if a site looks wrong, press Back to normal in that tab. It cannot change browser pages (chrome://), the Web Store or the built-in PDF viewer. Text inside images or canvas is a picture, so it does not change.

It runs on the pages you open (the browser words this as "read and change your data on all websites") because it has to change their text size. It does not read or send any page content. storage keeps your sizes (a tab's own size is kept in that tab and in the browser's session storage, cleared when the browser closes); activeTab lets the popup show the current site.