UNIVERSAL PARSER

A CPU-only document ingestion engine for RAG pipelines and AI agents. Parses 15+ file formats into a unified Pydantic schema with hierarchical chunking, adaptive layout fingerprinting, and a FastMCP server interface.

No GPU. No paid API. No recurring cost.

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Table of Contents

• Problem and Scope
• Related Work
• The One Original Contribution
• Supported Formats
• Installation
• Quickstart
• Output Schema
• API Reference
• Architecture
• Adaptive Layout Fingerprinting
• FastMCP Server
• Memory and Performance
• Benchmarks
• Limitations
• Contributing
• License

---

Problem and Scope

Feeding real-world documents into a RAG pipeline is harder than it looks.

A PDF is a stream of positioned drawing commands. Reading order breaks on multi-column layouts. Tables without visible borders are invisible to naive text extraction. Scanned pages have no machine-readable text. Every file format requires a different library, and those libraries return different data structures — making a consistent, type-safe downstream pipeline difficult to build.

This library handles the extraction and normalization layer: MIME sniffing, format routing, multi-column reading order reconstruction, two-pass table detection, OCR fallback, and output to a single validated Pydantic schema — for 15+ file formats, from a single parse(path) call, running entirely on CPU.

It does not do layout model inference, deep learning-based element classification, or PDF reconstruction at the visual rendering layer. For those capabilities, see Docling.

---

Related Work

Honest comparison with the tools a practitioner would actually evaluate before using this one.

Docling (IBM Research / Linux Foundation, MIT-adjacent license) Docling ships a trained document layout analysis model and a PDF table structure recognition model. Its classification quality on complex PDFs — dense academic papers, financial reports with borderless tables — is substantially higher than any heuristic-based approach including this one. If layout accuracy on complex PDFs is your primary concern, evaluate Docling first. It is CPU-capable and actively maintained by a funded team.

Marker (Apache-2.0) Marker uses a fine-tuned Surya OCR model and a layout segmentation model. It produces high-quality Markdown from PDFs, including scanned documents. Its OCR and rendering quality on scientific and academic PDFs is superior to the RapidOCR fallback used here. If your pipeline is primarily scientific PDFs, evaluate Marker first.

Unstructured (Apache-2.0, managed API available) Unstructured supports the broadest format coverage in the space (40+ formats) with optional hi-res partition mode and a managed API. If format breadth or managed infrastructure is a priority, evaluate Unstructured first.

Where this library differs:

Criterion	Docling	Marker	Unstructured	Universal Parser
Layout model inference	Yes (trained model)	Yes (Surya)	Optional (hi-res mode)	No (heuristics only)
Table structure recognition	Trained model	Limited	Optional	Heuristic (lattice + stream)
OCR quality	Good	Excellent	Good	Adequate (RapidOCR)
Format coverage	PDF, DOCX, XLSX, PPTX, HTML	PDF, images	40+ formats	15+ formats
Python version	3.9+	3.9+	3.9+	3.11+
Memory footprint	Moderate (model weights)	Higher (model weights)	Varies	<250 MB RSS (no model weights)
Per-template auto-tuning	No	No	No	Yes (see below)
MCP server interface	No	No	No	Yes

The heuristic approach used here extracts less accurately on complex layouts than Docling or Marker. The trade-off is zero model weights, lower memory, and a per-template configuration learning mechanism described in the next section.

---

The One Original Contribution

The piece of this library that does not exist in the same form in Docling, Marker, or Unstructured is the adaptive layout fingerprinting and per-template auto-tuner.

Many real RAG pipelines process the same document template repeatedly — the same invoice format thousands of times, the same SEC 10-K filing structure across years, the same internal report template across departments. In these workloads, the failure mode of heuristic extractors is predictable and reproducible: the same column threshold is wrong on the same template, every time.

The fingerprinter computes a content-agnostic 10x10 spatial occupancy grid from element bounding boxes, hashes it with SHA-256, and uses it as a stable template identity. The auto-tuner runs coordinate descent over the parameter space against a reference ground-truth document for that template, then persists the optimal configuration to a JSON cache. On subsequent files matching the same fingerprint (exact or fuzzy Cosine-Jaccard similarity above a configurable threshold), the cached configuration is applied automatically.

This is a focused, narrow contribution: it does not make the base extraction better than Docling on arbitrary documents. It reduces error variance on recurring templates where a heuristic extractor's default parameters are consistently wrong.

The ablation study validating this claim on a real document set is planned and tracked here.

---

Supported Formats

Category	Format	Extensions	Implementation
PDF	Native text	.pdf	pypdfium2 (Apache-2.0) with multi-column spatial clustering and font-size percentile heading hierarchy
PDF	Complex tables	.pdf	pdfplumber lattice and stream strategies with cell-density and dimensional boundary constraints
PDF / Image	Scanned documents	.pdf, .png, .jpg, .tiff, .bmp, .webp	RapidOCR (ONNXRuntime CPU) with OpenCV auto-orientation and deskew
Word	DOCX	.docx	python-docx heading hierarchy and table normalization
Excel	XLSX	.xlsx	openpyxl read-only streaming with merged-cell span replication
PowerPoint	PPTX	.pptx	python-pptx slide-by-slide shape, table, and title extraction
Legacy Office	Binary compound	.doc, .xls, .ppt	olefile OLE container parsing with xlrd and recursive asset unpacking
Web	HTML / XHTML	.html, .xhtml, .htm	selectolax Lexbor DOM parser with beautifulsoup4 fallback
E-book	EPUB	.epub	ebooklib spine-ordered chapter extraction with HTML sub-parsing
Structured	CSV / TSV	.csv, .tsv	Python csv.Sniffer dialect auto-detection
Structured	Parquet	.parquet	pyarrow zero-copy columnar record batch streaming
Structured	JSON / XML	.json, .xml	Recursive tree flattening and normalized schema mapping
Email	EML / MBOX	.eml, .mbox	email stdlib with recursive embedded attachment routing
Email	MSG (Outlook)	.msg	extract-msg (GPL-3.0 — see license section) with recursive attachment routing

---

Installation

Requires Python 3.11 or later.

pip install universal-doc-parser

With OCR support for scanned PDFs and raster images:

pip install "universal-doc-parser[ocr]"

With development tooling:

pip install "universal-doc-parser[dev]"

Using uv:

uv add universal-doc-parser
uv add "universal-doc-parser[ocr]"

System dependencies on Linux (for magic-byte MIME detection — optional, falls back to extension sniffing if absent):

# Ubuntu / Debian Bookworm (Python 3.10 era containers)
sudo apt-get install -y libmagic1t64

# Ubuntu / Debian Bullseye and earlier
sudo apt-get install -y libmagic1

# Fedora / RHEL
sudo dnf install -y file-libs

On macOS and Windows, MIME detection is handled through the Python package layer automatically.

---

Quickstart

Parse any document

from universal_parser import parse

doc = parse("path/to/annual_report.pdf")

print(f"Format:   {doc.metadata.file_type}")
print(f"Pages:    {doc.metadata.page_count}")
print(f"Elements: {len(doc.content_tree)}")
print(f"Has OCR:  {doc.metadata.has_scanned_pages}")

for element in doc.content_tree:
    if element.type == "heading":
        print(f"H{element.level}: {element.text}")
    elif element.type == "table":
        print(f"Table columns: {element.data.headers}")
    else:
        print(f"{element.type}: {element.text[:80]}")

Export to Markdown

from universal_parser import parse, to_markdown

doc = parse("contract.docx")
md = to_markdown(doc)
print(md)

Chunk for vector databases

from universal_parser import parse, to_chunks

doc = parse("technical_spec.pdf")
chunks = to_chunks(doc, max_tokens=512)

for chunk in chunks:
    print(f"Pages:            {chunk.page_numbers}")
    print(f"Heading context:  {' > '.join(chunk.headings)}")
    print(f"Estimated tokens: {chunk.estimated_tokens}")
    print(chunk.text)
    print("---")

Each chunk carries its full heading ancestry (H1 > H2 > H3) prepended as context. Retrieval models receive structurally anchored chunks rather than arbitrary token windows.

Export a knowledge graph

from universal_parser import parse, to_graph

doc = parse("research_paper.pdf")
graph = to_graph(doc)

for edge in graph.edges:
    print(f"{edge.source}  --[{edge.relation}]-->  {edge.target}")

Serialize to JSON

from universal_parser import parse

doc = parse("invoice.pdf")
print(doc.model_dump_json(indent=2))

---

Output Schema

Every supported format produces the same output structure.

{
  "schema_version": "1.0",
  "doc_id": "3f9a1c4e-8b21-4d77-b003-1234abcd5678",
  "metadata": {
    "file_name": "annual_report.pdf",
    "file_type": "pdf",
    "page_count": 42,
    "has_scanned_pages": false
  },
  "content_tree": [
    {
      "element_id": "a1b2c3d4-...",
      "type": "heading",
      "level": 1,
      "text": "Executive Summary",
      "page": 1,
      "bbox": { "x0": 72.0, "y0": 88.0, "x1": 540.0, "y1": 108.0 },
      "parent_id": null,
      "confidence": null
    },
    {
      "element_id": "e5f6g7h8-...",
      "type": "paragraph",
      "text": "Revenue increased by 24.8% year-over-year across the APAC region.",
      "page": 1,
      "bbox": { "x0": 72.0, "y0": 120.0, "x1": 540.0, "y1": 140.0 },
      "parent_id": "a1b2c3d4-..."
    },
    {
      "element_id": "i9j0k1l2-...",
      "type": "table",
      "page": 3,
      "data": {
        "headers": ["Region", "Revenue", "Growth"],
        "rows": [
          ["APAC", "$4.2B", "+24.8%"],
          ["EMEA", "$3.1B", "+11.2%"]
        ]
      },
      "markdown_repr": "| Region | Revenue | Growth |\n|---|---|---|\n| APAC | $4.2B | +24.8% |",
      "confidence": 0.97
    }
  ]
}

Schema field reference

Field	Type	Description
schema_version	string	Schema revision. Always "1.0" in this release.
doc_id	string	UUID v4 assigned at parse time.
metadata.file_name	string	Original filename including extension.
metadata.file_type	string	Normalized format: pdf, docx, xlsx, html, epub, csv, json, xml, parquet, image, eml, msg, mbox, pptx, doc.
metadata.page_count	int or null	Total pages. null for formats without page boundaries.
metadata.has_scanned_pages	bool	true if any page required OCR processing.
element_id	string	UUID v4 per element.
type	enum	One of: heading, paragraph, table, figure, list_item, code_block.
level	int or null	Heading depth 1-6. null for non-heading elements.
text	string or null	Plain text content. null for pure table elements.
page	int or null	1-indexed page number. null for formats without page structure.
bbox	BBox or null	{x0, y0, x1, y1} in PDF points (72 pt = 1 inch). null for non-spatial formats.
parent_id	string or null	element_id of the nearest ancestor heading.
data	TableData or null	{headers, rows} object. Set only when type == "table".
markdown_repr	string or null	Pre-rendered Markdown string.
confidence	float or null	Score in [0.0, 1.0]. Set for OCR output and table extractions.

---

API Reference

parse()

from universal_parser import parse

doc: Document = parse(path)

The main entry point. Accepts str or pathlib.Path. Performs format sniffing, routing, extraction, and Pydantic validation. Returns a fully validated Document.

Raises FileNotFoundError if the path does not exist. Raises ValueError for corrupt, unreadable, or unrecognized files. All internal extractor errors are caught and surfaced as ValueError with context.

---

to_markdown()

from universal_parser import to_markdown

md: str = to_markdown(doc)

Converts a Document to a single Markdown string. Headings render at their native # depth. Tables render as GitHub-Flavored Markdown pipe tables.

---

to_chunks()

from universal_parser import to_chunks

chunks: list[Chunk] = to_chunks(doc, max_tokens=512, overlap_tokens=50)

Hierarchical token-aware chunker.

Parameters:

• max_tokens - Maximum estimated tokens per chunk. Default: 512. Estimated at approximately 4 characters per token.
• overlap_tokens - Reserved for future sliding window chunking.

Chunk fields:

Field	Type	Description
chunk_id	string	Unique in the form {doc_id}-chunk-{n}.
text	string	Chunk text prefixed with Context: H1 > H2\n\n{content}.
headings	list[str]	Ordered heading ancestry from H1 to nearest ancestor.
element_types	list[str]	Deduplicated element types in this chunk.
page_numbers	list[int]	Sorted page numbers spanned by this chunk.
estimated_tokens	int	Estimated token count for the final chunk text.

Tables are kept intact within a single chunk wherever the budget allows. If a table exceeds the remaining budget, it starts a new chunk.

---

to_graph()

from universal_parser import to_graph

graph = to_graph(doc)
# graph.nodes: list[str]
# graph.edges: list of (source, relation, target) triples

Extracts a lightweight knowledge graph from heading-to-paragraph containment and term co-occurrence. Compatible with NetworkX and standard graph database import formats.

---

Architecture

Document Processing Pipeline

Input File
     |
     v
 [ Sniffer ]
 Magic-byte MIME detection via python-magic
 Falls back to file extension if MIME is ambiguous or library is unavailable
     |
     v
 [ Router ]
 FileType enum mapped to Extractor class registry
 Registry populated at import time via @register decorators
     |
     v
 [ Extractor ]
 Format-specific streaming generator
 Yields Element objects one at a time without buffering the full document
     |
     v
 [ Schema Normalizer ]
 Pydantic validation and UUID assignment
 Parent ID linking via heading ancestor stack
     |
     v
 [ Document ]
 Versioned, fully typed output object

Every extractor implements one method:

class BaseExtractor:
    def stream(self, path: Path) -> Iterator[Element]: ...

Adding a new format requires creating one file in universal_parser/extractors/ and one @register decorator call. Nothing else in the pipeline changes.

---

PDF Extraction Engine

PDF extraction runs in two cooperative passes over each page.

Pass 1 - Table Detection (extractors/pdf/tables.py)

Two strategies are attempted in sequence:

• Lattice: Detects tables with visible border lines. Uses pdfplumber cell boundary detection over explicit ruling line segments.
• Stream: Detects borderless tables using whitespace column alignment. A cell word-density heuristic (avg_words_per_cell <= 2.5) and a table height ratio constraint (table_h <= 0.40 * page_h) suppress false positives on paragraph-heavy pages.

Confidence scores are assigned based on cell uniformity and structural regularity.

Pass 2 - Text and Heading Extraction (extractors/pdf/native.py)

• Character positions are read from the PDFium character map for every non-table region.
• Font sizes across the page are collected and percentile thresholds computed. Elements at or above the 95th percentile are classified H1, the 85th percentile H2, and the 75th percentile H3. All remaining text is classified as paragraphs.
• Multi-column detection: the page midpoint is computed from the spatial distribution of text element centroids. Elements are partitioned into left column, right column, and full-width zones. Full-width headers are yielded first, followed by the entire left column top-to-bottom, then the entire right column top-to-bottom, then full-width footers.
• Pages with zero extractable characters fall back to RapidOCR.

---

Adaptive Layout Fingerprinting

Documents that follow recurring templates - invoices, financial reports, regulatory filings - can be registered once and reused across thousands of files with cached optimal extraction parameters.

Fingerprinting (adaptive/fingerprint.py)

Each document is represented as a content-agnostic 10x10 spatial occupancy grid. Every element's bounding box is normalized to the standard coordinate space (612 x 792 pt) and quantized to a grid cell. The matrix, combined with element type distribution proportions, is hashed with SHA-256 to produce a stable fingerprint.

from universal_parser.adaptive import compute_fingerprint

doc = parse("invoice_template.pdf")
fp = compute_fingerprint(doc)
print(fp.hash_digest)  # SHA-256 hex string
print(fp.spatial_grid)  # 10x10 occupancy matrix

Template Configuration Cache (adaptive/config_cache.py)

A thread-safe LRU cache maps fingerprints to extractor configuration dicts. Supports exact SHA-256 lookup, fuzzy Cosine-Jaccard similarity lookup (default threshold 0.85), and atomic JSON persistence to disk.

from universal_parser.adaptive import TemplateConfigCache

cache = TemplateConfigCache(cache_file="template_cache.json")
cache.set(fp.hash_digest, {"column_threshold": 0.45, "table_strategy": "lattice"})
config = cache.get(fp.hash_digest)

Auto-Tuner (adaptive/tuner.py)

A coordinate-descent optimizer iterates over the parameter space and minimizes a composite error metric against a reference ground-truth document. Mathematical guardrails prevent convergence to degenerate configurations.

from universal_parser.adaptive import auto_tune

optimal_config = auto_tune(
    template_path="path/to/template.pdf",
    reference_path="path/to/ground_truth.json",
)
cache.set(fp.hash_digest, optimal_config)

The ablation study measuring extraction accuracy with auto-tuning on vs off across a real set of recurring templates is in progress and will be published here when complete with methodology and sample sizes disclosed.

---

Observability System

Metrics Collector (observability/metrics.py)

A process-level singleton MetricsCollector records telemetry for every parse() invocation. Thread-safe via threading.Lock. Each ParseEventMetric captures: file_name, file_type, page_count, element_count, duration_ms, has_scanned_pages, and an anomalies list.

from universal_parser.observability import MetricsCollector

for event in MetricsCollector().get_events():
    print(f"{event.file_name}: {event.duration_ms:.1f} ms | {event.element_count} elements")

Telemetry Dashboard (observability/dashboard.py)

Exports a standalone HTML file with interactive charts. No external network dependencies at render time.

from universal_parser.observability import export_dashboard

export_dashboard(output_file="parser_telemetry.html")

---

FastMCP Server

Universal Parser exposes a FastMCP server for AI agent and Claude Desktop integration over stdio.

Run the server:

uv run python -m universal_parser.mcp.server

Available tools:

Tool	Parameters	Description
parse_document	file_path: str, output_format: str	Parse any local document. output_format: "markdown", "chunks", or "json".
list_supported_formats	none	Returns all supported format identifiers as a sorted list.

Configure in Claude Desktop (claude_desktop_config.json):

{
  "mcpServers": {
    "universal-doc-parser": {
      "command": "uv",
      "args": [
        "run",
        "--with",
        "universal-doc-parser",
        "python",
        "-m",
        "universal_parser.mcp.server"
      ]
    }
  }
}

After restarting Claude Desktop, Claude can invoke parse_document against any local file path.

---

Memory and Performance

The streaming generator architecture bounds memory consumption regardless of document length. No page is held in memory after it is yielded.

The numbers below are from the memory benchmark suite (benchmarks/memory_profile.py) running on an Intel Core i7, 16 GB RAM, no GPU. These are heuristic estimates from a controlled synthetic document, not profiled runs on varied real-world corpora. Real-world peak RSS will vary depending on document complexity, table density, and OCR engagement.

Document Size	Peak RSS Memory	Processing Time
100 pages	~150 MB	~5 seconds
500 pages	~165 MB	~24 seconds
1,000 pages	~180 MB	~49 seconds

The 250 MB RSS hard limit is asserted in the benchmark suite on every CI push:

uv run python benchmarks/memory_profile.py

---

Benchmarks

What exists today

The benchmark suite at benchmarks/run_llm_benchmark.py compares this library's extraction output against live API calls to Gemini 2.5 Flash, GPT-4o, DeepSeek V3, Qwen 2.5 72B, Llama 3.3 70B, and other models accessible via the Google AI Studio and OpenRouter free tiers.

14 of the 15 rows in the original benchmark table were live API results. The two Claude rows (Claude 3.5 Sonnet and Claude 3 Opus) were simulated estimates — Anthropic does not expose Claude on any free API tier, and the original README did not disclose this distinction. Those rows have been removed from published tables until a properly labeled live run can be completed.

Run the benchmark suite yourself:

# Offline mode — simulates responses, zero cost, no API keys required
uv run python benchmarks/run_llm_benchmark.py

# Live mode — runs real API calls against Gemini and OpenRouter models
GEMINI_API_KEY=your_key OPENROUTER_API_KEY=your_key \
  uv run python benchmarks/run_llm_benchmark.py --live

What is planned

The benchmark work that would make this project defensible — and which does not yet exist — is:

1. Head-to-head against Docling, Marker, and Unstructured on the same document corpus (target: SEC EDGAR 10-K filings and PubTables-1M) with disclosed sample sizes and a documented scoring methodology.

2. Auto-tuning ablation study: Extraction accuracy with fingerprint-based auto-tuning ON vs OFF, across a set of 20-30 recurring invoice and filing templates, with sample sizes and error metric definition stated explicitly.

These are the two experiments that would either validate or invalidate the claims this project is making. Until they exist, treat the current benchmark numbers as directional indicators, not validated results.

---

Limitations

These are known failure modes, not edge cases.

• Complex PDF layouts: On multi-column academic papers and dense financial reports with borderless tables, Docling's trained layout model will outperform the heuristic approach used here. If layout accuracy on complex PDFs is the primary requirement, use Docling.
• Scanned document quality: The RapidOCR fallback performs adequately on clean scans. On degraded, skewed, or low-resolution scans, Marker's Surya-based OCR pipeline will produce substantially better results.
• Python version requirement: This library requires Python 3.11+, which excludes some deployment environments. Docling, Marker, and Unstructured support Python 3.9+.
• MSG parsing license: The extract-msg dependency carries a GPL-3.0 license. MSG parsing is therefore subject to GPL-3.0 copyleft terms — see the license section for the full implication.
• Memory numbers are heuristic estimates: The memory table above was produced from a controlled synthetic document. Real-world peak RSS will vary.
• Benchmark numbers are not externally validated: No one outside of the author has run the full benchmark suite on the full dataset yet. Treat published numbers accordingly.

---

Contributing

All pull requests must pass the full quality gate before review.

Adding a new format:

1. Create universal_parser/extractors/<category>/<format>_extractor.py
2. Implement BaseExtractor.stream(path) as a generator
3. Add @register(FileType.YOUR_FORMAT) to register it in the router
4. Import the module in universal_parser/__init__.py
5. Add fixture files in tests/fixtures/<format>/ — at minimum three samples including one deliberately complex or malformed file
6. Write tests in tests/test_<format>.py asserting schema correctness, content accuracy, and graceful error handling
7. Add a docs/CHANGELOG.md entry

Pull requests without fixture files and corresponding tests will not be reviewed.

Code standards:

• Pass uv run ruff check . with zero errors
• Format with uv run ruff format .
• No new AGPL-licensed dependencies. All additions must carry MIT, Apache-2.0, or BSD licenses

Full local quality gate:

uv sync --all-extras
uv run ruff check .
uv run ruff format .
uv run pytest -v
uv run python benchmarks/memory_profile.py
uv run python benchmarks/test_messy_document.py
uv run python benchmarks/run_llm_benchmark.py

---

License

This project is licensed under the MIT License. See LICENSE for the full text.

License note on MSG support: The extract-msg dependency used for Outlook .msg parsing is licensed under GPL-3.0. If you parse .msg files in a closed-source product, the GPL-3.0 copyleft terms apply to that use. All other runtime dependencies carry permissive licenses (MIT, Apache-2.0, BSD, LGPL-3.0). If your use case requires a fully permissive dependency tree, you can exclude .msg parsing by not calling parse() on .msg files and removing extract-msg from your installation.

Dependency	License	Purpose
pypdfium2	Apache-2.0	PDF text extraction (Google Chromium PDFium engine)
pdfplumber	MIT	PDF table extraction
pydantic	MIT	Schema validation and serialization
python-docx	MIT	Word document parsing
openpyxl	MIT	Excel spreadsheet parsing
pyarrow	Apache-2.0	Parquet columnar streaming
selectolax	MIT	HTML DOM parsing
ebooklib	LGPL-3.0	EPUB parsing
rapidocr-onnxruntime	Apache-2.0	CPU OCR inference
opencv-python-headless	Apache-2.0	Image preprocessing
pillow	HPND	Image handling
python-pptx	MIT	PowerPoint parsing
xlrd	BSD-3-Clause	Legacy XLS binary parsing
olefile	BSD-2-Clause	OLE compound file parsing
extract-msg	GPL-3.0	Outlook MSG email parsing -- see note above
beautifulsoup4	MIT	HTML fallback parser
mcp	MIT	FastMCP server interface

The previous dependency on PyMuPDF / fitz (AGPL-3.0) was removed in v0.1.0 and replaced with pypdfium2 (Apache-2.0).