Code Spell Checker

Detects misspelled words in code by splitting camelCase identifiers into constituent words and matching each against language-specific dictionaries, enabling detection of typos in variable names like 'getUserNme' without false positives on legitimate camelCase patterns. Uses offline dictionary matching rather than ML models, processing the current file in real-time as the developer types.

Provides spell checking in 40+ languages through a modular architecture where the core extension includes English (US) by default, and additional language dictionaries are installed as separate VS Code extensions. Each language add-on extends the base spell checker with language-specific dictionaries and rules, allowing developers to switch languages via the `cSpell.language` configuration setting.

Allows developers to define custom dictionaries at the project, workspace, or user level to whitelist domain-specific terms, acronyms, brand names, and technical jargon that would otherwise be flagged as misspellings. Custom dictionaries are stored in configuration files and merged with the base language dictionaries during spell checking, enabling teams to maintain a shared vocabulary of approved terms.

Integrates with VS Code's Quick Fix UI (lightbulb icon) to display spelling correction suggestions directly in the editor. When a misspelled word is detected, developers can position their cursor on the underlined word and press Ctrl+. (or Cmd+. on Mac) to open a dropdown menu of suggested corrections, then click to apply the fix with a single action. This integrates into the standard VS Code diagnostics and code action pipeline.

Continuously monitors the currently open file in VS Code and displays misspelled words as inline squiggly underlines (red wavy lines) in real-time as the developer types. Diagnostics are published to VS Code's diagnostics pipeline and appear in the Problems panel, allowing developers to see all spelling errors in the current file at a glance. Spell checking runs asynchronously to avoid blocking the editor.

Applies spell checking selectively to different code scopes: code comments (both single-line and multi-line), string literals, and identifiers (variable/function names). The spell checker distinguishes between these scopes and applies appropriate rules — for example, camelCase splitting is applied to identifiers but not to comments. This scope awareness reduces false positives by avoiding spell checking in contexts where misspellings are intentional or irrelevant.

Integrates spell checker configuration into VS Code's standard settings system using the `cSpell.*` configuration namespace. Developers can configure spell checking behavior via VS Code's Settings UI, `settings.json` file, or workspace-level configuration files. Configuration options include language selection, custom dictionaries, and other spell checker parameters, allowing per-user, per-workspace, and per-project customization.

Performs spell checking by comparing words against a pre-built dictionary loaded into memory at extension startup. The dictionary is stored as a compiled data structure (format unknown — likely a trie or hash set for O(1) lookup) and does not require network access. Validation is performed locally on the user's machine, ensuring privacy and fast response times. The extension does not use machine learning models or external APIs; it relies entirely on static dictionary matching.

The extension applies spell checking selectively to supported file types and languages. Explicitly supported languages include TypeScript, JavaScript, and plain text. Additional language support is provided through installed language pack extensions. The extension uses VS Code's language mode detection to determine which files to check. Spell checking scope (which parts of a file to validate) may vary by language — for example, TypeScript files check comments and strings, while plain text files check all content.

The extension aims to minimize false positives by using dictionary frequency data and context heuristics (exact approach not documented). Common words are prioritized over rare words, and context clues (e.g., word position, surrounding tokens) may influence whether a word is flagged. The documentation states the goal is 'keeping the number of false positives low,' but specific algorithms or thresholds are not disclosed. Users can add words to custom dictionaries to further reduce false positives.