Local-First • Offline AI

A local-first writing assistant for clearer drafts.

Proofread, rewrite, format, and export your prose while keeping your text entirely on your device. Lexicon combines inline LanguageTool grammar rules with optional local AI models without requiring cloud accounts or subscriptions.

Download for Desktop
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Lexicon Workspace
Lexicon application preview

Click the preview above or watch the full product launch video on YouTube (with audio)

Complete Feature Set

Designed for quiet, focused writing

An editorial workspace organizing proofreading rules, local AI transformations, LaTeX math, and clean manuscript exports into simple, un-cluttered modules.

LanguageTool Engine Clarity Score

Real-time Grammar, Spelling & Readability Score

Spot mechanics, grammar, and spelling issues as you type. Flagged items feature clear inline marks like misspelled words and suggested revisions with synchronized suggestion cards, 1-click Apply/Dismiss, and real-time Clarity & Readability scores.

Keyboard Driven Efficiency

Slash Commands & Instant Block Insertion

Execute operations without leaving your keyboard. Type / on any new line to trigger insertion menus for Headings (H1-H6), Code Blocks, Tables, Task lists, and LaTeX equations.

Math & Code

LaTeX Math, Syntax & Formatting

Insert inline math $E=mc^2$ or block LaTeX $$\int_{0}^{\infty} e^{-x^2} dx$$ with live editor preview, syntax-highlighted code blocks, inline code const lex = new Lexicon(), task lists, and font/line spacing controls.

Eco & Private Local LLM

Offline AI (10+ Local Use Cases)

Run 10+ local AI tools: Refinement (rewrite, concise), Structure (summaries, key points, lists, tables), and 9 Tone Shifts (Professional, Academic, Friendly, Casual, Formal, Empathetic, Persuasive, Humorous, Playful). 100% on-device zero cloud data leaks, zero datacenter water usage, and zero server latency.

Focus Mode

Distraction-Free Canvas

Collapse sidebars and UI panels with a single keystroke (Ctrl + Shift + F) to write on a clean, calm, editorial canvas.

Custom Dictionary

Personal Vocabulary

Save custom brand names, domain terminology, and unique jargon to your personal dictionary so LanguageTool never flags them as spelling errors.

Import & Export

Clean PDF & Multi-Format Export

Import `.md`, `.txt`, and `.html` drafts. Export to clean manuscript PDFs (with app UI chrome and squiggles removed), raw Markdown, Plain Text, or HTML.

Local Storage Data Protection

Local Profile Storage & Model-Preserving Updates

Local auto-save prevents lost work. Application updates install seamlessly over the app while preserving your downloaded AI models, custom settings, and personal dictionary intact in your local profile data.

100% Private
User Guide & Walkthrough

How to Use Lexicon

A complete tutorial walking through proofreading, local AI rewrites, slash commands, and shortcuts.

STEP 01

Onboarding & Setup

Complete the 4-step onboarding wizard on first launch:

  1. Set your English dialect preference (e.g. English (US) or English (UK)).
  2. Choose your opt-in local AI model: Light (0.8 GB) or Standard (1.4 GB), or connect Ollama.
  3. Note: Proofreading and editing work immediately without downloading an AI model!
STEP 02

Proofreading & Grammar Review

Inline grammar and spell checking run automatically as you type:

  • Click Proofread in the top bar to run a full document pass.
  • Hover over flagged squiggles or review suggestion cards in the right Review Panel.
  • Click Apply to accept a fix, Dismiss to ignore, or add unknown words to your Personal Dictionary.
STEP 03

Local AI Rewrites & Tone Shifts

Transform your text with offline AI models:

  • Highlight any paragraph or sentence in your document.
  • Open the left Actions panel and select a transform tool: Rewrite, Make Concise, Summary, or Key Points.
  • Select a tone shift: Professional, Academic, Friendly, Casual, Formal, Empathetic, Persuasive, Humorous, or Playful.
  • Review the diff output in the right panel and click Apply.
STEP 04

Slash Commands, Math & Shortcuts

Speed up drafting without leaving the keyboard:

  • Type / on a new line to open the slash menu for Headings, Code Blocks, Tables, and Tasks.
  • Type $E=mc^2$ for inline LaTeX math or insert block equations with live previews.
  • Toggle Focus Mode to hide sidebars for an uncluttered writing view.
Privacy by Design

100% Local-First & Private

Lexicon is built from the ground up to ensure your words, documents, and writing habits remain strictly on your local hardware.

Local Profile Storage

100% PRIVATE

Your drafts, personal dictionaries, custom settings, and writing analytics are stored in your local user profile. No cloud sync, mandatory account creation, or background telemetry.

Embedded LanguageTool Engine

ZERO LATENCY

Grammar, spelling, and style rule passes run deterministically on your local CPU via an embedded runtime. Your prose is never uploaded to remote cloud APIs for proofreading.

Offline LLM Inference

LOCAL AI

Lexicon's AI writing assistant executes GGUF models (Light 0.8 GB or Standard 1.4 GB) directly on your device via native sidecar processes or your existing Ollama server.

Complete Data Ownership

OPEN STANDARDS

Import and export documents seamlessly in `.md`, `.txt`, `.html`, or `.pdf`. Delete downloaded AI models or clear local data at any time with a single click.

Cloud Assistants vs. Lexicon Architecture

Why offline processing protects your privacy and intellectual property.

OFFLINE FIRST

Cloud Writing Tools

  • Transmits full document text over the public internet
  • Requires mandatory account creation & login
  • May train AI models on user drafts and text inputs
  • Fails completely when offline or traveling

Lexicon Local Architecture

  • 100% offline — zero bytes of document text transmitted
  • No user accounts, subscriptions, or login forms
  • Zero telemetry logging; local model weights stored on disk
  • Works seamlessly on airplanes, remote locations, and offline
Setup Walkthrough & Assistance

Setup & Support

Step-by-step installation guide, OS launch verification, and issue tracking.

3-Step Setup Walkthrough

From download to your first draft in under 2 minutes.

1. DOWNLOAD

Get the Installer

Click Download for Desktop at the top of this page to get the installer for your OS (Windows `.exe` or macOS `.dmg`).

2. VERIFY

First Launch Pass

Run the installer. If your OS displays a SmartScreen or Gatekeeper warning, follow the quick 1-click override steps below.

3. START WRITING

Begin Drafting

Open Lexicon, choose your optional model, and start typing. Grammar fixes and suggestion cards appear automatically!

Windows (SmartScreen)

Windows

If Windows SmartScreen shows "Windows protected your PC" during initial installation:

  1. Click More info under the warning prompt.
  2. Click Run anyway to complete installation.

macOS (Gatekeeper)

macOS

If macOS shows "Lexicon cannot be opened because it is from an unidentified developer":

  • Option 1 (GUI): Control-click (right-click) Lexicon.app → select Open → click Open.
  • Option 2 (System Settings): Open System Settings > Privacy & Security → scroll down and click Open Anyway.
  • Option 3 (Terminal): Run xattr -cr /Applications/Lexicon.app in Terminal.

Found an issue or have a suggestion?

Submit bug reports and feature proposals directly on GitHub.

Report a Bug Request a Feature