Hearing your own writing read back is the fastest way to catch a doubled word, a missing “not” or a sentence that runs on too long. Your eyes skip over those; your ears do not.
The line under the text box gives the length and a rough listening time, based on about 150 words a minute at normal speed. Paste 300 words and it says about 2 minutes.
Where do the voices come from?
From your operating system and your browser. The page does not bring voices of its own, so the list differs between your phone and your laptop, and even between two browsers on the same computer. Each entry shows the voice’s name, its language code and either “on this device” or “online”. If your system’s default voice is among them, it is selected to start with.
What if the text is not in English?
The menu lists English voices unless you ask for more. For French, Spanish or any other language, tick “Show voices for all languages” and choose a voice whose code matches, such as fr-FR. An English voice reading French sounds wrong, so this choice matters more than the speed.
Why one sentence at a time?
Some online voices in Chrome stop a long passage partway through, so each sentence is handed to the voice on its own, and a sentence longer than 200 characters is cut at a comma or a space. While it plays you see “Reading sentence 3 of 12” and can Pause, Resume or Stop. After Stop, Read aloud starts again from the beginning.
What can’t it do?
It cannot save audio, change how a single word is pronounced, or switch voices halfway through a text. If a name comes out wrong, spell it the way it sounds; the voice reads exactly what is in the box. And if your browser has no speech support at all, the page says so instead of showing an empty menu.