Offline Writing Quality Checker: Lint Without Internet

Internet connectivity isn't always reliable. You're on a flight drafting documentation, working from a remote location with spotty connectivity, or simply prefer working offline to avoid distractions. But when you need to check writing quality, most grammar checkers and linting tools require active internet connections.

Cloud-based grammar checkers like Grammarly need constant connectivity to process text. Even local tools often require online package managers, update checks, or remote rule downloads. For technical writers, developers, and content creators who work offline, this dependency creates frustrating gaps in workflow.

ProseLint Web solves this with complete offline functionality. After a one-time setup, you can lint markdown, check style guides, and maintain documentation quality without any internet connection—permanently.

Why offline writing tools matter

Reliable offline capability isn't just a convenience—it's essential for many workflows:

Travel and remote work

When you're working on the go:

Flight writing sessions: Long flights are productive writing time, but in-flight WiFi is expensive, slow, or unavailable. Offline linting lets you draft and refine documentation at 35,000 feet.

Remote locations: Working from cabins, rural areas, or international locations with unreliable connectivity shouldn't prevent quality checking.

Roaming cost avoidance: International travel with limited data plans makes cloud-based tools expensive. Offline capability eliminates data usage for linting.

Focus and distraction reduction

Sometimes offline is intentional:

Distraction-free writing: Disconnecting from the internet improves focus. Offline linting tools mean you don't sacrifice quality checks for concentration.

Deep work sessions: Extended writing sessions benefit from offline mode that prevents notifications, email checks, and browsing distractions.

Library and coffee shop work: Avoiding public WiFi security risks while maintaining access to professional writing tools.

Security and compliance

Offline capability serves security needs:

Air-gapped environments: Secure facilities, classified work, and high-security contexts require offline tools that never initiate network connections.

Data security policies: Organizations that prohibit external network connections for content processing need verifiable offline tools.

Privacy assurance: Offline operation proves your content isn't being transmitted—not through logs or policies, but through the impossibility of network communication when disconnected.

Reliability and performance

Offline tools are simply more reliable:

No dependency on external services: Cloud-based tools fail when servers are down, APIs are unreachable, or rate limits are hit. Offline tools work regardless of external service status.

Consistent performance: No latency from network requests, server processing, or API rate limiting. Offline linting is as fast as your local hardware, every time.

Long-term availability: Cloud services shut down, pricing models change, or features get deprecated. Offline tools that cache locally continue working independently of vendor decisions.

How ProseLint Web achieves complete offline functionality

ProseLint Web uses modern browser technologies to enable genuine offline capability:

Progressive Web App architecture

ProseLint Web is built as a Progressive Web App (PWA), which means:

Service workers cache assets: A service worker is a JavaScript file that runs in your browser and intercepts network requests. ProseLint Web's service worker caches all static assets (HTML, CSS, JavaScript, Vale WASM binary) so they load instantly from local cache rather than the network.

App-like behavior: Once cached, ProseLint Web functions like a native application. Open the URL without internet, and the cached app loads from browser storage.

Install to home screen: On mobile devices and supported browsers, you can "install" ProseLint Web to your home screen for quick access, even without connectivity.

WebAssembly binary caching

Vale's linting engine is a WebAssembly binary that processes your content:

One-time download: The first time you visit ProseLint Web, the WASM binary (about 6.2MB compressed) downloads and caches using the Cache API.

Persistent storage: Browsers persist cached WASM indefinitely unless you manually clear cache. The binary remains available for all future offline sessions.

Offline execution: Once cached, the Vale WASM binary runs entirely from browser memory without any network access. All processing is local and offline.

Rule package storage in IndexedDB

Style guide packages (Microsoft, Google, Red Hat, etc.) store in IndexedDB:

Download packages once: The first time you select a style guide, the rule package downloads as a ZIP file, extracts with JavaScript, and saves to IndexedDB.

Persistent offline access: IndexedDB is permanent browser storage (unless manually cleared). Downloaded packages remain available indefinitely for offline use.

Multiple packages supported: Download all the style guides you need while online. All cached packages work offline simultaneously.

Zero network dependency after setup

After initial caching:

Disconnect from the internet completely
Open ProseLint Web by navigating to the bookmarked URL
App loads from cache without any network requests
Select cached style guide packages from IndexedDB
Lint content using local WASM execution
All features work exactly as they do online

You can verify this behavior using browser DevTools: with the Network tab open and internet disconnected, every ProseLint Web feature functions perfectly with zero network requests.

Setting up ProseLint Web for offline use

Getting offline-ready takes just a few minutes while you have connectivity:

Step 1: Initial visit and caching

While connected to the internet:

Navigate to ProseLint Web editor in your browser
Wait for full load: Let the page completely load, which triggers caching of the service worker, static assets, and Vale WASM binary
Verify caching: Open browser DevTools → Application tab → Cache Storage and IndexedDB to see cached assets

Step 2: Download rule packages

While still online:

Select each style guide package you want to use offline:
- Microsoft Writing Style Guide
- Google Developer Documentation Style Guide
- Red Hat Documentation Style Guide
- GitLab Documentation Style Guide
- Any other packages you need
Wait for download confirmation: Package downloads are a few MB each and cache in IndexedDB automatically
Verify package caching: Check DevTools → Application → IndexedDB → vale-packages to see stored packages

Step 3: Test offline functionality

Before relying on offline mode:

Disconnect from internet or enable Airplane mode
Navigate to ProseLint Web URL from bookmarks or history
Confirm app loads from cache without network access
Paste sample content into the editor
Select a cached package and lint
Verify all features work: Quick fixes, issue navigation, editor functionality

If everything works offline, you're ready for offline writing sessions.

Step 4: Bookmark and install (optional)

Make offline access convenient:

Browser bookmark: Add ProseLint Web to bookmarks for quick access from the URL bar offline

PWA installation: On supported browsers and mobile devices, use the "Install" or "Add to Home Screen" option to create an app-like shortcut

Desktop shortcut: Create a desktop shortcut to your browser with ProseLint Web URL for instant offline access

Offline workflow strategies

Here's how to integrate offline linting into your writing workflow:

Pre-travel preparation

Before flights or trips to areas with poor connectivity:

Update rule packages: While online, revisit ProseLint Web to ensure you have the latest package versions cached
Test offline: Disconnect and verify everything works before your trip
Download alternative packages: Cache multiple style guides if you work on different projects with different standards
Sync other tools: If you use Vale CLI locally, sync packages there too for consistency

Offline writing sessions

During offline work:

Draft content in your preferred offline editor (local text editor, Markdown app, etc.)
Periodic linting: Copy sections to offline ProseLint Web and lint as you complete major portions
Fix issues immediately: Address style problems while writing context is fresh
Continuous iteration: Re-lint after fixes to verify corrections and catch new issues

Return-to-online workflow

When connectivity returns:

Final online lint: Optionally re-lint with freshest package versions (though offline versions remain valid)
Sync to version control: Commit polished documentation to repositories
Refresh packages: Update cached rule packages if you'll be offline again soon

Comparing offline capabilities: ProseLint Web vs. alternatives

Most writing tools struggle with offline use:

Cloud-based grammar checkers (Grammarly, ProWritingAid)

Offline capability: None. These tools require active internet connections to upload content to servers for processing. Without connectivity, they're completely non-functional.

Workaround: None available. The architecture depends on cloud processing.

Vale CLI (local installation)

Offline capability: Excellent after installation. Vale CLI runs completely locally and works offline indefinitely.

Trade-offs: Requires local installation, configuration, and command-line familiarity. Not available on systems where you can't install software (borrowed computers, locked-down corporate systems).

Best for: Developers and technical writers comfortable with CLI tools and able to install local software.

ProseLint Web (browser-based)

Offline capability: Complete after one-time caching. Works indefinitely offline with no installation required.

Trade-offs: Requires browser with PWA support. Initial setup needs connectivity for caching.

Best for: Writers who want offline capability without local installation, or who work across multiple devices without consistent local setup.

Traditional text editor plugins

Offline capability: Varies by plugin. Some work offline, many require online API access.

Trade-offs: Tied to specific editors. Offline capability often limited to basic spell-check rather than comprehensive style linting.

Advanced offline features

ProseLint Web's offline mode includes sophisticated capabilities:

Quick-fix automation

Even offline, ProseLint Web provides:

One-click fixes: Many style issues include suggested replacements you can apply with a single click Regex-based corrections: Complex edit actions (adding text, removing patterns, transforming structure) work offline Batch corrections: Apply multiple fixes across your document without network access

Multi-format support

Offline linting handles:

Markdown: Including GitHub-flavored markdown with tables, task lists, strikethrough
MDX: Markdown with JSX components for modern documentation frameworks
AsciiDoc: Technical documentation format with full syntax support
HTML: Direct HTML content with prose extraction
Plain text: Unformatted text files

All format parsing and transformation happens offline using cached WASM.

Editor features

The offline editor includes:

Syntax highlighting: For markdown, MDX, and other supported formats Line numbers: Precise issue location tracking Issue decorations: Visual highlighting of problems directly in the editor File upload: Drag-and-drop file loading (files never leave your device) Persistent state: Your content and settings save in IndexedDB, surviving browser restarts

Privacy advantages of offline capability

Offline functionality provides inherent privacy guarantees:

Provable local processing: When you verify the app works offline, you've proven your content never transmits to external servers. This isn't a policy promise—it's a technical impossibility when disconnected.

Air-gapped security: For sensitive content, offline capability enables true air-gapping. Disconnect from networks entirely, lint confidential content, and reconnect later without ever exposing drafts.

Zero data retention concerns: Cloud services retain uploaded content subject to their policies. Offline tools never upload content, so there's nothing to retain, access, or breach.

Troubleshooting offline issues

If offline mode doesn't work as expected:

App doesn't load offline

Check browser cache: DevTools → Application → Cache Storage should show ProseLint Web assets Try clearing and re-caching: Online, clear browser cache, revisit ProseLint Web to re-cache Verify PWA support: Ensure your browser supports service workers and Cache API (all modern browsers do)

Packages missing offline

Check IndexedDB: DevTools → Application → IndexedDB → vale-packages should show downloaded packages Re-download packages: While online, select packages again to ensure they cache Storage quota issues: Some browsers limit storage. Check if quota is exceeded and clear unneeded data

Linting fails offline

Verify WASM loaded: Check DevTools Console for WASM initialization errors Try refreshing: Close and reopen ProseLint Web to reload cached assets Test with simple content: Verify offline linting works with basic markdown before complex documents

Future offline enhancements

Upcoming offline improvements may include:

Background package updates: Automatically update cached rule packages when online without user intervention Offline package management: Add, remove, and manage packages in offline mode with syncing when connectivity returns Cross-device sync: Optional encrypted sync of packages and preferences across devices (still client-side, no cloud processing)

Conclusion: offline capability enables uninterrupted quality

Internet connectivity shouldn't dictate when you can check writing quality. Whether you're working from a flight, a remote cabin, a secure facility, or intentionally offline to focus, your writing deserves professional linting.

ProseLint Web delivers complete offline functionality without compromise. After a one-time setup while online, every feature works indefinitely without connectivity. Professional style guides, comprehensive format support, quick-fix automation—all available offline, all private, all reliable.

Set up ProseLint Web for offline use today and experience writing quality tools that work anywhere, anytime, regardless of internet availability.

Resources

ProseLint Web editor — offline-capable writing quality checker
Vale CLI — local installation for offline command-line linting
Progressive Web Apps (PWA) overview — understanding PWA technology
Service Worker API documentation — how offline caching works