Code Documentation Generators: TypeDoc, JSDoc, Sphinx, rustdoc, and Modern Alternatives

Code Documentation Generators: TypeDoc, JSDoc, Sphinx, rustdoc, and Modern Alternatives

Code documentation generators read your source code -- its types, comments, and structure -- and produce browsable reference documentation. The good ones make your API discoverable. The bad ones produce walls of auto-generated text that nobody reads. The difference comes down to two things: how well you comment your code, and which tool you choose. Here's a comparison of the major generators and the modern alternatives competing with them.

Language-Specific Generators

TypeDoc (TypeScript)

TypeDoc is the standard documentation generator for TypeScript. It reads your type annotations and JSDoc comments, then produces HTML or Markdown output.

bun add -d typedoc

Configuration (typedoc.json):

{
  "entryPoints": ["src/index.ts"],
  "entryPointStrategy": "expand",
  "out": "docs/api",
  "exclude": ["**/*.test.ts", "**/*.spec.ts"],
  "excludePrivate": true,
  "excludeInternal": true,
  "plugin": ["typedoc-plugin-markdown"],
  "readme": "none",
  "name": "My Library API",
  "navigation": {
    "includeCategories": true,
    "includeGroups": true
  }
}

bunx typedoc

What you write:

/**
 * Creates a rate limiter using a sliding window algorithm.
 *
 * @param maxRequests - Maximum requests allowed in the window
 * @param windowMs - Window duration in milliseconds
 * @returns A rate limiter instance
 *
 * @example
 * ```typescript
 * const limiter = createRateLimiter(100, 60_000);
 * if (limiter.check("user-123")) {
 *   // Request allowed
 * }
 * ```
 *
 * @remarks
 * The sliding window approach provides smoother rate limiting than
 * fixed windows. Memory usage is O(n) where n is the number of
 * unique keys being tracked.
 */
export function createRateLimiter(
  maxRequests: number,
  windowMs: number,
): RateLimiter {
  // ...
}

What you get: A navigable reference with the function signature, parameter descriptions, return type, example code, and remarks -- all extracted from the source. TypeDoc inherits TypeScript's type information, so even undocumented parameters show their types.

The Markdown plugin (typedoc-plugin-markdown) is essential. Instead of generating a standalone HTML site, it outputs Markdown files that you embed in Docusaurus, Starlight, or any other documentation framework. This lets your API reference live alongside your prose documentation in one site.

Output quality: Directly proportional to your JSDoc comments. With thorough comments and @example tags, TypeDoc output is excellent. Without comments, you get a type reference that's technically accurate but unhelpful -- functions listed with their signatures and nothing else.

JSDoc (JavaScript)

JSDoc predates TypeScript and generates documentation from specially formatted comments in JavaScript files.

npm install -g jsdoc

Configuration (.jsdoc.json):

{
  "source": {
    "include": ["src/"],
    "includePattern": ".+\\.js$",
    "excludePattern": "(node_modules|test)"
  },
  "opts": {
    "destination": "docs/api",
    "recurse": true,
    "template": "node_modules/clean-jsdoc-theme"
  },
  "plugins": ["plugins/markdown"]
}

/**
 * Parses a cron expression into a structured schedule.
 * @param {string} expression - Standard cron expression (5 fields)
 * @returns {CronSchedule} Parsed schedule object
 * @throws {CronParseError} If the expression is invalid
 * @example
 * parseCron("0 */2 * * *") // Every 2 hours
 */
function parseCron(expression) { /* ... */ }

Verdict: If you're writing TypeScript, use TypeDoc instead -- it understands your types natively. JSDoc is only relevant for plain JavaScript projects that aren't migrating to TypeScript. The default JSDoc theme looks dated; use clean-jsdoc-theme or better-docs for modern output.

Sphinx (Python)

Sphinx is the dominant documentation generator in the Python ecosystem. It powers the official Python docs, Django docs, and most major Python library documentation.

pip install sphinx sphinx-rtd-theme
sphinx-quickstart docs

Configuration (docs/conf.py):

project = "My Library"
extensions = [
    "sphinx.ext.autodoc",      # Generate docs from docstrings
    "sphinx.ext.napoleon",     # Support Google/NumPy docstring style
    "sphinx.ext.intersphinx",  # Cross-reference other projects
    "sphinx.ext.viewcode",     # Link to source code
]
html_theme = "furo"  # Modern, clean theme (pip install furo)
autodoc_member_order = "bysource"
autodoc_typehints = "description"

Writing docstrings:

def create_connection(
    host: str,
    port: int = 5432,
    ssl: bool = True,
    timeout: float = 30.0,
) -> Connection:
    """Create a database connection with automatic retry.

    Establishes a connection to the specified host with exponential
    backoff retry logic. Connections are pooled by default.

    Args:
        host: Database hostname or IP address.
        port: Database port number.
        ssl: Whether to use TLS encryption.
        timeout: Connection timeout in seconds.

    Returns:
        An active database connection.

    Raises:
        ConnectionError: If the connection cannot be established
            after all retry attempts.

    Example:
        >>> conn = create_connection("db.example.com")
        >>> conn.execute("SELECT 1")
    """

Sphinx with autodoc reads these docstrings and produces reference pages. The napoleon extension lets you write in Google or NumPy docstring style instead of reStructuredText.

Output quality: Excellent when you use a modern theme (Furo, PyData Sphinx Theme) and write thorough docstrings. The default alabaster theme looks outdated. The Read the Docs theme (sphinx-rtd-theme) is recognizable but starting to show its age.

Strengths: Powerful cross-referencing (:func:create_connection``), intersphinx linking to other projects' docs, versioning support, extensive plugin ecosystem.

Weaknesses: reStructuredText is verbose and less intuitive than Markdown. MyST-Parser adds Markdown support, but it's an extra layer. Build times can be slow for large projects. Configuration is Python code, which is flexible but non-standard.

rustdoc (Rust)

rustdoc is built into the Rust toolchain. Run cargo doc and get documentation for your entire crate.

cargo doc --open --no-deps

/// Creates a new thread pool with the specified number of workers.
///
/// # Arguments
///
/// * `size` - Number of worker threads. Must be greater than 0.
///
/// # Panics
///
/// Panics if `size` is 0.
///
/// # Examples
///
/// ```
/// let pool = ThreadPool::new(4);
/// pool.execute(|| println!("Hello from a worker!"));
/// ```
pub fn new(size: usize) -> ThreadPool {
    // ...
}

What makes rustdoc special: Documentation examples are compiled and run as tests (cargo test runs doc examples). This means your examples never go stale -- if the API changes, the doc test fails. Every language should steal this idea.

Output quality: Consistently good because Rust's culture emphasizes documentation. The default output is clean and functional. The search works well.

Javadoc (Java)

Javadoc ships with the JDK. It's been generating documentation since 1995 and it shows -- the output format is dated, but it's deeply embedded in Java tooling.

/**
 * Processes a batch of records with configurable parallelism.
 *
 * <p>Records are partitioned across worker threads. Failed records
 * are collected and returned for retry handling.
 *
 * @param records the records to process, must not be null
 * @param parallelism number of worker threads (1-64)
 * @return result containing processed count and failed records
 * @throws IllegalArgumentException if parallelism is out of range
 * @since 2.3.0
 */
public BatchResult processBatch(List<Record> records, int parallelism) {

Modern alternatives: Consider Dokka for Kotlin projects or the MkDocs/Writerside approach for combined prose + API reference.

Doxygen (C/C++)

Doxygen generates documentation from annotated C, C++, Python, Java, and other source files.

/**
 * @brief Allocates a buffer from the memory pool.
 *
 * Returns a buffer of at least @p size bytes. The actual allocation
 * may be larger due to alignment requirements.
 *
 * @param size Minimum buffer size in bytes
 * @param alignment Memory alignment (default: 16 bytes)
 * @return Pointer to allocated buffer, or nullptr on failure
 *
 * @note Thread-safe. Multiple threads can allocate concurrently.
 * @warning Returned buffers must be freed with pool_free(), not free().
 */
void* pool_alloc(size_t size, size_t alignment = 16);

Configuration (Doxyfile):

PROJECT_NAME = "MyLib"
OUTPUT_DIRECTORY = docs
GENERATE_HTML = YES
GENERATE_LATEX = NO
EXTRACT_ALL = YES
INPUT = src/ include/
FILE_PATTERNS = *.h *.cpp
HAVE_DOT = YES
CALL_GRAPH = YES

Output quality: Functional but visually dated. The call graphs (via Graphviz) are useful for understanding code structure. For modern C++ projects, consider Doxygen for extraction paired with a custom HTML theme or a tool like Standardese.

Modern Alternatives

Mintlify

Mintlify is a hosted documentation platform that combines handwritten prose documentation with auto-generated API reference from OpenAPI specs.

What it does well: Beautiful defaults out of the box. The API reference includes interactive "Try It" panels. Analytics show which pages are popular and where users drop off. Git-based workflow -- push Markdown and Mintlify builds and deploys.

What it doesn't do: Mintlify doesn't read your source code. It's not a code documentation generator in the traditional sense. You write prose docs and reference OpenAPI specs. If you need auto-generated reference from TypeScript or Python source, you still need TypeDoc or Sphinx.

Pricing: Free tier (limited pages), Startup at $120/month, Growth at $400/month.

ReadMe

ReadMe is another hosted documentation platform focused on API documentation. It reads OpenAPI specs and generates interactive reference docs with code samples in multiple languages.

What it does well: Developer hub with API reference, guides, changelogs, and a community forum. API request logging shows real-time usage. Automatically generates code snippets in curl, Python, JavaScript, Go, Ruby, and more.

What it doesn't do: Like Mintlify, it doesn't generate docs from source code. It's a documentation platform, not a code documentation generator.

Pricing: Free for small projects. Startup at $99/month. Enterprise pricing available.

Output Quality Comparison

Recommendations

TypeScript library: TypeDoc with the Markdown plugin, embedded in your documentation site (Starlight or Docusaurus). Write JSDoc comments on every public export. Skip standalone JSDoc entirely.

Python project: Sphinx with the Furo theme and napoleon extension. Use Google-style docstrings. Add autodoc for API reference and write guides as separate .md files with MyST-Parser.

Rust crate: cargo doc is all you need. Write doc comments with examples on every public item. The doc-test feature is Rust's secret weapon for documentation quality.

REST API: Generate docs from your OpenAPI spec. Use Mintlify if you want hosting and interactivity. Use Redoc or Scalar for self-hosted options. These are better than hand-writing API reference.

Multi-language project: Pick the best generator for each language and unify the output in a single documentation site. TypeDoc Markdown + Sphinx Markdown builders + Docusaurus or Starlight as the host.

General principles:

• The generator matters less than the comments. No tool produces useful documentation from uncommented code.
• Generate reference docs, write guides by hand. These are different skills solving different problems.
• Run doc generation in CI. Broken builds catch missing exports, invalid examples, and broken cross-references.
• Embed generated docs in your main site rather than hosting a separate auto-generated site. One URL for all documentation.