Speech Utterance Tester

The Speech Utterance Tester is a free online tool that leverages the Web Speech API (SpeechSynthesis) built into modern browsers. It reads your text aloud while highlighting each word in real-time, making it perfect for pronunciation practice, language learning, proofreading, and accessibility testing. All processing happens locally on your device — no text is ever sent to any server.

The tool uses the onboundary event from the SpeechSynthesisUtterance API, which fires at each word or phoneme boundary during speech. By tracking the charIndex provided by this event, the tool maps the current speech position to the corresponding word in your text and applies a visual highlight with a smooth CSS transition. This gives you precise, real-time feedback on which word is being spoken.

The Web Speech API is supported in Google Chrome (desktop & Android), Microsoft Edge, Safari (desktop & iOS), Firefox, and Opera. Chrome and Edge generally offer the widest selection of high-quality voices, including Google's neural TTS voices. Safari on iOS may have fewer voice options. If speech synthesis doesn't work, ensure your browser is updated and that you've granted any necessary audio permissions.

Available voices depend on your browser and operating system. Most systems include voices for English (US, UK, Australian, Indian), Spanish, French, German, Italian, Japanese, Chinese, Korean, Portuguese, Russian, and many more. Chrome on desktop typically offers 30+ voices including Google's premium neural voices. Use the voice dropdown to browse all available options, grouped by language.

Use the intuitive sliders in the control panel. Speed ranges from 0.25x (very slow) to 3x (very fast), with 1x being normal speaking speed. Pitch adjusts the voice tone from 0.1 (deep) to 2.0 (high). Volume controls output loudness from 0% to 100%. All settings take effect immediately on the next playback. These controls let you fine-tune the speech for optimal clarity and learning comfort.

Common causes include: 1) Your browser doesn't support the Web Speech API (try Chrome or Edge). 2) On iOS Safari, speech synthesis may require a user gesture (tap the Play button). 3) Your device's audio is muted or volume is too low. 4) No voices are installed on your system — check the voice dropdown; if it's empty, try restarting your browser. 5) Some privacy-focused browser extensions may block the API. Try disabling extensions temporarily.

No. All speech synthesis processing happens entirely on your device using the browser's built-in speech engine. Your text is never transmitted to any server, stored, or logged. This tool operates 100% client-side, ensuring complete privacy. You can use it offline as long as the voices are cached by your browser. This makes it safe for confidential or sensitive text content.

This tool is excellent for language learners. Tips: Slow down the speed (0.5x-0.7x) to catch every syllable. Follow along with the word highlighting to connect spoken sounds with written words. Use the Prev/Next Word buttons to replay challenging words. Switch between different voices (e.g., US vs. UK English) to train your ear for various accents. Practice shadowing by reading aloud along with the highlighted words to improve pronunciation and fluency.