Custom AI Prompts for Dictation: A Power Guide

Dictation used to just type what you said. On a modern Mac, an on-device AI can also rewrite it: fixing punctuation, cutting filler, and shaping the words into an email, a list, or a commit message. Custom AI prompts are how you take control of that step, and they turn good dictation into finished text.

What a custom AI prompt actually does

Every dictation pipeline starts the same way: your microphone captures audio, and a speech model turns it into text. On BlaBlaType that recognition runs locally, using on-device models like Whisper and NVIDIA's Parakeet. The raw output is accurate, but it is still raw: filler words, false starts, and no real structure.

The AI cleanup step is where a prompt comes in. A prompt is the instruction handed to the on-device model along with your transcript. A default cleanup might just fix punctuation and remove "um" and "uh". A custom prompt goes further: it can say "rewrite this as a polite email", "format as a bulleted checklist", or "make this a one-line git commit message in imperative mood". Same voice input, very different text out. If you want the fuller story of that transformation, our guide on going from rambling to ready to send walks through it end to end.

Anatomy of a good dictation prompt

Prompts do not need to be long. On a Mac, dictation happens in the flow of work, so the model benefits from clear, compact instructions rather than an essay. Four ingredients cover almost every case:

• A role. "You are a precise copy editor" or "You are a senior engineer" sets the register instantly.
• An output format. Email, bullet list, single sentence, meeting note. Be explicit.
• A tone. Formal, friendly, neutral, terse. Pick one and do not contradict it later.
• One or two rules. "Remove filler words", "keep under three sentences", "do not add greetings".

Because BlaBlaType supports 90+ languages, it is worth remembering that the cleanup follows the language you spoke in unless you tell it otherwise. If you dictate in Spanish and want English out, say so in the prompt. And for accessibility use cases, structured prompts are a real help: many people who find typing difficult, including those with dyslexia as described by the British Dyslexia Association, get cleaner drafts when the AI handles formatting for them.

Prompt recipes by task

The fastest way to learn is to steal working examples. Here is how the same feature adapts across common tasks, with the trade-off each recipe makes.

Notice the last row. Sometimes the right prompt is a light touch. When you are capturing a quote or a raw idea, "fix punctuation only" protects your exact words. A common power-user setup is to keep one prompt per context and switch between them, so a message in your editor becomes a commit line while the same style of speech in Mail becomes a paragraph. For a wider look at running your whole Mac by voice, see our guide to hands-free computing on a Mac.

Prompts versus the custom dictionary

Prompts and the custom dictionary solve different problems, and mixing them up is the most common mistake. A prompt controls how the text reads: tone, length, structure. The custom dictionary controls how specific words are spelled: a colleague's name, a product, an acronym, a bit of jargon the recognizer would otherwise guess wrong. If your teammate "Xiuying" keeps coming out as "Shoeing", no prompt will reliably fix that. The dictionary will. We cover the setup in teaching dictation your own words. Use both together: the dictionary gets the vocabulary right, the prompt makes it read right.

Why on-device makes prompts better

The quiet advantage here is privacy. With BlaBlaType, both the speech recognition and the AI cleanup run on your Mac, powered by Apple Intelligence. That means your custom prompt and your dictated content are processed locally: audio and transcripts never leave the device. There is no per-minute cloud bill, and prompts work the same whether you are on a plane or at your desk.

Practically, that also means you can dictate sensitive material through a custom prompt without a second thought. Client notes, legal drafts, unreleased product names: they stay on your machine. Most people speak around three to four times faster than they type, so once your prompts are dialed in, you get finished, private text at the speed of talking. You can compare the built-in option in our piece on Apple Dictation versus BlaBlaType, and see plan details on the pricing page.