Most AI writing tools work the same way under the hood: what you type is sent to a server, a large model processes it, and a response comes back over the network. That's true whether the tool rewrites a paragraph, drafts an email, or just suggests the next few words. It's also the part people notice least — until they think about what "sent to a server" actually means for a personal message or a client email.

An offline AI writing assistant flips that model: the language model runs directly on your PC, so there's no server in the loop at all. This article covers how that's technically possible, what you trade off, and where Typeahead fits as an example.

How On-Device AI Writing Actually Works

Cloud AI tools typically run large models — tens of billions of parameters — on data-center hardware, because that's the only place such models fit. On-device tools use much smaller, compressed models that fit in a few hundred megabytes to a few gigabytes of storage and run on a normal PC's CPU or GPU. The trade for a smaller footprint is a somewhat smaller model — but for a narrow task like predicting the next phrase in a sentence, a compact model can be genuinely fast and accurate without needing the scale of a general-purpose chatbot.

The inference itself — the actual process of generating a suggestion from a model — happens through a local runtime. Typeahead, for example, uses llama.cpp, an open-source engine for running language models efficiently on consumer hardware, paired with a small multilingual model called Qwen 3. No request ever leaves the machine because there's nowhere for it to go — the model and the runtime are both sitting on your disk.

No server round-trip

Suggestions are computed on your CPU/GPU, not sent to a data center and back — nothing to intercept, log, or store remotely.

Works without a connection

Once the model is downloaded, the assistant keeps working with Wi-Fi off — on a flight, on a train, anywhere.

No account needed

There's no login tied to your writing, because there's no server keeping track of who's using it.

The Trade-Offs, Honestly

Local models are smaller than the largest cloud models, and smaller generally means less capable at open-ended tasks like long-form generation or complex reasoning. For a narrow, well-defined job — predicting how the sentence you're already writing is likely to continue — that gap matters much less than it would for, say, writing an essay from a one-line prompt. The model also takes up disk space (Typeahead's three options range from about 400 MB to 2.5 GB) and needs a one-time download before it can run, unlike a cloud tool that's ready the moment you sign in.

When offline wins: if what you're typing is sensitive — client correspondence, personal messages, anything under an NDA — the privacy trade-off is the whole point. If you need a model to draft a five-page report from scratch, a larger cloud model will generally do a more thorough job.

Typeahead as a Working Example

Typeahead is a system-tray utility that suggests the rest of the sentence you're typing, in almost any Windows desktop app: WhatsApp, Telegram, Slack, Chrome, Edge, Firefox, Outlook, Thunderbird, Word, Notepad, Notepad++, and VS Code's chat and text panes. It runs on a local LLM (Qwen 3 via llama.cpp) or on custom autocorrect rules — fully offline, with no account and no text telemetry. Custom snippet autocorrect and dictionary-based autocomplete work even before a model is downloaded.

Three model sizes are available depending on the trade-off you want between speed and quality: fast (~400 MB, the default), balanced (~1.1 GB), and maximum (~2.5 GB). The model is multilingual, covering 100+ languages, and suggests in whatever language you're actively typing. Suggestions appear as ghost text at the caret; press Tab (default, configurable) to accept one. It's a one-time $9.99 purchase through the Microsoft Store with a 7-day free trial, and password managers and financial apps are excluded from suggestions by default.

For a related, non-AI approach to faster typing, GagarinSoft also makes Text Replacements, a typed-trigger text expander — useful if you want exact, predictable snippets rather than AI-generated suggestions for a given phrase.

Frequently Asked Questions

What does "offline AI" actually mean?
It means the language model runs on your own device instead of a remote server. There's no network request carrying your text anywhere — the model, the computation, and the result all stay local.
Is a local model as good as a cloud model like ChatGPT?
For open-ended tasks, large cloud models generally have an edge because of their size. For a narrow task like predicting the next phrase in a sentence you're already writing, a small local model can perform well without needing that scale.
Does Typeahead ever send my text anywhere?
No. Typed text never leaves the device. The only network activity is downloading a model or checking for app updates — there's no account and no text telemetry.
How much disk space does a local AI writing assistant need?
For Typeahead, between roughly 0.4 GB and 2.5 GB depending on which of the three models you choose — fast, balanced, or maximum quality.
Can it work without downloading a model at all?
Yes, partially. Custom snippet autocorrect and dictionary-based autocomplete work immediately, before any model is downloaded. Full sentence-continuation suggestions require a model.
What are the system requirements?
Windows 10 or later, or Windows 11, with 8 GB of RAM and 0.4–2.5 GB of free disk space depending on the model chosen.

Get Typeahead

One-time purchase, no subscription. Windows 10 / Windows 11. 7-day free trial.

 Get it on Microsoft Store