HeyGen Voice Text to Speech

HeyGen Voice Text to Speech — AI Text-to-Speech

What is HeyGen Voice Text to Speech?

HeyGen Voice Text to Speech turns a written script into natural, expressive spoken audio with HeyGen's in-house voice engine. Send text (up to 5,000 characters) and a voice ID, and the API returns a ready-to-use audio file in one synchronous call. The voice can be any of HeyGen's hundreds of stock catalog voices, or a voice you previously created with HeyGen Voice Clone. Its signature strength is authentic delivery: emphasis, emotion, character, and pacing held across a full script, so sentence stress follows meaning instead of drifting into a flat, robotic read. HeyGen Voice debuted at #1 on Artificial Analysis' Controlled Voice Arena, ahead of Qwen-Audio-3.1-TTS-Plus and ElevenLabs' Eleven v4 Turbo — a board that holds the voice constant by scoring every model on the same eight cloned reference voices, so the ranking reflects the cloned-voice path.

Key Features

• •Hundreds of HeyGen stock catalog voices plus your own clones, all reachable from a single endpoint.
• •Human-like prosody: correct question intonation, naturally spoken numbers and names, and emotion that shifts across sentences.
• •Multilingual delivery: set an optional language code (en, pt-BR, zh-HK) or let the engine auto-detect it from the text.
• •Speed control from 0.5 to 2 for stock voices; expressiveness from 0 to 1 for cloned voices.
• •Up to 5,000 characters per request, returned as one audio file.

Best Use Cases

HeyGen Voice fits any job where a consistent, listenable voice matters: AI assistants and customer-service lines — where it ranks #1 on the controlled arena — plus e-learning narration, explainer and product voiceover, audiobooks, IVR prompts, accessibility voiceover, and avatar pipelines. In testing, one stock voice carried a first-person discovery monologue from tension to relief, a second stock voice re-read a script in a different timbre, and a native German voice delivered a localized tour, all from the same endpoint. Because this engine also powers HeyGen avatars and video translation, teams can keep one brand voice across standalone audio and on-screen talent.

Prompt Tips and Output Quality

Write multi-sentence text with real punctuation; questions, numbers, and names render naturally. Leave engine unset — premade catalog voices reject an engine pin. For stock voices, adjust speed between 0.5 and 2; expressiveness applies to cloned voices only. Set a language code for non-English scripts, or rely on auto-detection. Spell tricky brand or shorthand terms out, since expanding abbreviations is the engine's weaker spot. Output in testing was clean and clear.

How to Use HeyGen Voice Text to Speech

HeyGen Voice Text to Speech reads a script in a HeyGen voice and returns an audio file. You supply two things: the text to speak and a voice_id. The voice can be one of HeyGen's hundreds of stock catalog voices, or a voice you created with HeyGen Voice Clone (that clone stays private to the workspace that made it). Write multi-sentence text with natural punctuation — questions, numbers, and proper nouns are pronounced correctly, and delivery changes with the words, so you rarely need markup for a lifelike read. Keep each request under 5,000 characters, and spell out abbreviations or unusual brand names, since expanding shorthand is the engine's weaker area.

Recommended Settings

• •Stock voice (start here): set voice_id to a catalog voice and leave engine and language unset — the engine picks its own default and auto-detects the language. Use speed 0.5 to 2 to pace the read.
• •Force a language: set a language code such as de, pt-BR, or zh-HK, paired with a voice that speaks it.
• •Cloned voice: set voice_id to a clone you made in HeyGen Voice Clone, keep speed at 1, and use expressiveness 0 to 1 (around 1 for lively reads, near 0.2 for calm narration). Expressiveness applies to clones only; stock voices use the default.

Example voices to try

Each example below ran end to end at the settings shown, on HeyGen stock catalog voices; the voice, speed, and language carried straight into the audio.

• •Expressive English narration (default). Prompt: "Forty-one nights on the mountain, and still nothing. Then, at 3:12 in the morning, the screen lit up. Could this really be it? I called Dr. Okafor at the Atacama station, my hands shaking so hard I could barely hold the phone. We checked it twice, then a third time - and yes, it was real. After three years, we had finally found it." The read moved from weary to tense to relieved, with natural number and name pronunciation. Tip: vary punctuation to cue the pacing.
• •Second stock voice. Prompt: "In the back room, Mara folds each sheet by hand, then stitches the signatures with waxed linen thread. The press is a hundred and forty years old, and it still bites a clean, crisp line into the cotton paper." read in a warm female catalog voice. Tip: swap voice_id alone to re-brand the same script without a clone.
• •Faster delivery (speed 1.3). Prompt: "On the line, a bare frame becomes a finished bicycle in just under nine minutes. Robots torque each bolt to the exact spec, a laser checks the wheel is true to half a millimeter." at speed 1.3 ran noticeably brisker while staying natural. Tip: speed is stock-voice-only, range 0.5 to 2.
• •German (language de). Prompt: "Sie stehen im großen Saal des alten Rathauses, erbaut 1898 aus Eichenholz und Sandstein. Schauen Sie nach oben: Das Deckengemälde zeigt die vier Jahreszeiten." with language set to de gave a native-sounding German read. Tip: set language to force a market; otherwise it auto-detects.

Also built for: "narrate an e-learning module in one steady catalog voice", "voice an AI assistant or customer-service line", and "localize one script across markets by swapping the voice and the language code".

Where do voice IDs come from?

From HeyGen's stock voice catalog, or a clone you made with HeyGen Voice Clone.

Does this model clone voices?

No — it speaks. Create clones with HeyGen Voice Clone; a clone stays private to the workspace that made it.

Do I need to set an engine?

No. Leave engine unset; premade catalog voices reject a pin and the engine chooses its own default.

Which languages are supported?

Many — set a language code such as pt-BR or zh-HK, or let the model auto-detect it from the text.

How long can a script be?

Up to 5,000 characters per request.