bytesense 0.1.1

Fast, accurate charset/encoding detection. Zero ML. Zero dependencies. Optional Rust acceleration.

Charset detection that stays fast, honest, and dependency-free.

_{Author: Oğuzhan Kır · GitHub · Documentation}

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bytesense reads raw bytes and tells you which encoding likely produced them—without shipping neural nets, without pulling in other Python packages at install time, and with an explainable why on every result. It is designed as a modern alternative to chardet and charset-normalizer for teams that want predictable performance and a small install footprint.

If you already use chardet.detect() or charset_normalizer.detect(), you can swap in bytesense.detect() with minimal code churn.

Comparison with chardet & charset-normalizer

Same idea as the charset-normalizer README: a feature matrix and measured accuracy on the bundled suites, so you can see where bytesense stands—not hand-wavy marketing.

Feature matrix

Feature	Chardet	Charset Normalizer	bytesense
Fast	✅	✅	✅
Universal¹	❌	✅	✅
Reliable without distinguishable standards	✅	✅	✅
Reliable with distinguishable standards	✅	✅	✅
License	MIT	MIT	MIT
Native Python (no C extension required)	✅	✅	✅
Optional native acceleration	—	—	Rust (pip install "bytesense[fast]")
Detect spoken language	✅	✅	✅
Explainable detection (why)	Partial	Rich metadata	Yes (always)
Streaming-first API	Limited	Via API patterns	StreamDetector
Wheel size (typical)	~500 kB	~150 kB	Small (pure Python + tables)
Custom codecs via stdlib registration	❌	✅	✅ (same codecs model)

¹ Universal in the charset-normalizer sense: coverage follows what your Python build exposes through codecs as decode candidates—not a fixed “99 encodings” count on every platform.

Accuracy (bundled tests, three-way)

Numbers below are from the same ./scripts/compare_libraries.sh run the CI exercises: chardet, charset-normalizer, and bytesense on identical inputs. Strict = detected codec name matches the reference (after codecs.lookup aliases). Functional = decoded Unicode matches the reference encoding (multiple labels can count if they decode to the same text—same spirit as charset-normalizer’s comparisons).

39-case suite (synthetic + charset-normalizer’s published data/ samples, expected labels aligned with their tests):

Package	Strict	Functional
bytesense	100% (39/39)	100% (39/39)
charset-normalizer	92.3% (36/39)	97.4% (38/39)
chardet	79.5% (31/39)	97.4% (38/39)

24-case hard stress (paragraph-sized, ambiguous SBCS / CJK / UTF-16 / ISO-2022 — benchmarks/test_hard_scenarios.py):

Package	Strict	Functional
bytesense	83.3% (20/24)	100% (24/24)
charset-normalizer	41.7% (10/24)	58.3% (14/24)
chardet	70.8% (17/24)	91.7% (22/24)

Updated March 2026 — CPython 3.12, chardet 7.x, charset-normalizer 3.4.x, bytesense 0.1.0. Your CPU and dependency versions will differ; re-run ./scripts/compare_libraries.sh to refresh.

Speed (pytest-benchmark, same machine snapshot)

Rough single-thread means (pytest benchmarks/test_bench_detection.py, speed filter; your numbers will differ):

Sample (from_bytes / detect)	bytesense	chardet
utf8_bom	~4 µs	~104 µs
utf8_ascii_only	~46 µs	~114 µs

UTF-8 with BOM is an early exit in bytesense; chardet still runs its full probe. Profile your own payloads.

How to reproduce

pip install -e ".[dev]"
python scripts/build_fingerprints.py
python scripts/fetch_cn_benchmark_samples.py   # CN `data/` mirrors into benchmarks/data/cn_official/
./scripts/compare_libraries.sh                   # prints the tables above (accuracy + hard stress)

Options: ./scripts/compare_libraries.sh --no-fetch (no download), --no-hard (skip 24-case stress). Full benches: ./scripts/run_all_benchmarks.sh.

Fingerprint script: Lines like utf_16 “skipped” are normal — UTF-16/32 are handled via BOM / null-byte rules, not the single-byte histogram table.

Troubleshooting fetch_cn_benchmark_samples.py (SSL on macOS): Use .venv/bin/python scripts/.... certifi is in [dev]. If HTTPS still fails: Install Certificates.command for your Python, or python scripts/fetch_cn_benchmark_samples.py --insecure as a last resort.

Installation

pip install bytesense                 # pure Python — always works
pip install "bytesense[fast]"       # same API; uses Rust wheel when available for your platform

Test PyPI (pre-release smoke test): after publishing to test.pypi.org, install with an extra index so pip can fetch build tools from PyPI:

pip install --index-url https://test.pypi.org/simple/ --extra-index-url https://pypi.org/simple/ bytesense

CLI

bytesense ships with a small CLI for files on disk.

usage: bytesense [-h] [-v] [-m] [--version] FILE [FILE ...]

positional arguments:
  FILE              File(s) to analyse

optional arguments:
  -h, --help        show this help and exit
  -v, --verbose     Include the ``why`` field in JSON (``confidence_interval`` is always shown)
  -m, --minimal     Print only the detected encoding name
  --version         Show version and exit

bytesense ./README.md
bytesense -m ./README.md
python -m bytesense.cli --version

stdout is JSON (one object per file, or a list when multiple files and not -m):

{
  "encoding": "utf_8",
  "confidence": 0.98,
  "confidence_interval": [0.93, 1.0],
  "language": "English",
  "alternatives": [],
  "bom_detected": false,
  "chaos": 0.02,
  "coherence": 0.41,
  "byte_count": 2048,
  "path": "/absolute/path/to/file"
}

Use -v to add the human-readable why string to each object.

Python

Full result object

from bytesense import from_bytes, from_path

result = from_path("notes.txt")
print(result.encoding, result.confidence, result.language)
print(result.why)

Streaming

from bytesense import StreamDetector

det = StreamDetector()
for chunk in response.iter_content(1024):
    det.feed(chunk)
    if det.confidence >= 0.99:
        break
print(det.encoding, det.language)

Repair mojibake

from bytesense import repair

garbled = "été"   # UTF-8 read as Latin-1
result = repair(garbled)
if result.improved:
    print(result.repaired)    # "été"
    print(result.chain)       # ("latin_1", "utf_8")
    print(result.improvement) # e.g. 0.34

Stream from HTTP

from bytesense import detect_stream
import urllib.request

with urllib.request.urlopen("https://example.com") as resp:
    result = detect_stream(
        iter(lambda: resp.read(1024), b""),
        stop_confidence=0.99,
    )
print(result.encoding)

HTML/XML hints

from bytesense import best_hint, from_bytes

html = b'<meta charset="cp1252"><p>Hëllo</p>'
hint = best_hint(html, headers={"Content-Type": "text/html"})
result = from_bytes(html)
print(hint, result.encoding)

Multi-encoding documents

from bytesense import detect_multi

# Example: bytes from a legacy .eml or mixed scrape
your_bytes = b"..."  # replace with your document
result = detect_multi(your_bytes)
print(f"Uniform encoding: {result.is_uniform}")
for seg in result.segments:
    print(f"  [{seg.start}:{seg.end}] {seg.encoding} — {seg.text[:40]!r}")

Drop-in detect()

from bytesense import detect

print(detect(b"hello"))  # {"encoding", "confidence", "language"}

More detail: MkDocs site · API · Quick start · Examples

Why bytesense

• Decode as late as possible. Histograms, BOMs, and null-byte layout often rule out whole families of encodings before you spend CPU on full decodes.
• Shortlist, then verify. Cosine similarity against pre-generated fingerprints (see scripts/build_fingerprints.py) keeps the expensive “mess + coherence” phase on a handful of candidates.
• No black boxes. No training step, no weights to tune, no network calls—just tables and statistics you can inspect.
• Rust is optional. pip install bytesense never requires a compiler; Rust only accelerates hot paths when a wheel matches your platform.

How it works (short)

1. Fingerprint the byte distribution and compare to pre-computed vectors.
2. Decode only the shortlisted encodings (strict), in a controlled order.
3. Mess — score how “garbled” the decoded text looks (printable ratio, bigrams, etc.).
4. Coherence — score language plausibility using character-frequency priors.
5. Rank and return the best hypothesis plus a human-readable why.

Known limitations

• Very short inputs (dozens of bytes) are inherently ambiguous; any detector will guess.
• Mixed-language text can confuse language coherence.
• Like any heuristic detector, adversarial or random binary data may yield a best-effort encoding with low confidence.

Contributing

Issues and PRs are welcome: CONTRIBUTING.md · Issues

License

MIT — see LICENSE.

Copyright © Oğuzhan Kır.