Richard Nesbitt

Adds a fixed container with 3 buttons to the right hand side of your webpage. Allows users to increase, decrease, or reset font sizes for their optimal viewing experience.
This plugin uses localStorage to save the viewers preferences, and loads on every page so their font changes carry over as they go deeper into your site. As long as the users cache persists, their preferences will be saved for when they return.

Font Resize – Accessibility Compliance

Adds a text resize widget on the front end of your site.

UserWay

Web accessibility can seem complex and overwhelming if you don’t know where to start.
Let us make it easier, and, to coin a phrase, more accessible for everyone. UserWay’s Accessibility Widget creates a simpler and more accessible browsing experience for your users while increasing compliance with WCAG 2.1, ATAG 2.0, European EN 301 549, ADA, & Section 508 requirements.
UserWay’s Accessibility Widget will strengthen any weak areas that could cause accessibility issues on your site. We are proud to say that a significant number of websites are more accessible today thanks to UserWay.
UserWay’s Accessibility Widget makes smart modifications to elements on your site that are identified as being non-compliant, that may prevent keyboard-only navigation, or are in violation of ADA regulations.
Install UserWay’s Accessibility Widget today. 
After installing UserWay’s Accessibility Widget, you will receive login instructions to the widget via email.
ADA & WCAG 2.1 Compliance 
UserWay’s best-in-class accessibility solutions move your site towards ADA and WCAG 2.1 compliance.
Shield Against Lawsuits 
Increasing your accessibility provides real, sustainable improvement for all users, and protects you from accessibility-related lawsuits.
Improve SEO, Boost Traffic 
Make your commitment clear: a more inclusive site for everyone expands your demographic and boosts your SEO.
<iframe loading="lazy" class="youtube-player" width="560" height="315" src="https://www.youtube.com/embed/gBh5x-C_Ow0?version=3&rel=1&showsearch=0&showinfo=1&iv_load_policy=1&fs=1&hl=en-US&autohide=2&wmode=transparent" allowfullscreen="true" style="border:0;" sandbox="allow-scripts allow-same-origin allow-popups allow-presentation allow-popups-to-escape-sandbox"></iframe>

Accessibility by UserWay

There is no such thing as a quick fix (one button click) for accessibility. This widget may be, at best, work like a small band aid. 

An accessible website needs amongst other things, semantic HTML5, good keyboard accessibility, meaningful (handwritten) alt texts for images and good screen reader feedback. This widget cannot provide that.

The claim: “WCAG 2.1 AA Compliance is Within Reach” is a very bold one.

Design and build a website from the start with accessibility in mind.
The WordPress Accessibility Handbook is a good starting point.

Note to the developer:
The button to activate the widget doesn’t get keyboard focus. So can’t be activated by keyboard users.

If you want to know more, I recommend reading:
Reminder: Accessibility can’t be solved automatically by Joe Dolson.

There is no such thing as a quick accessibility fix

UserWay’s Accessibility Widget creates a simpler and more accessible browsing experience for your users.

Font Resize – Accessibility Compliance vs Accessibility by UserWay