language_tool_python: Python wrapper for LanguageTool

language_tool_python is a Python interface/wrapper to LanguageTool, an open-source grammar, style, and spell checker.

It can:

• run a local LanguageTool Java server,
• call LanguageTool public API,
• call your own remote LanguageTool server,
• be used from Python code and from a CLI.

Default local download target: LanguageTool 6.8.

Documentation

• Docs: https://language-tool-python.readthedocs.io/en/latest/
• Changelog: CHANGELOG.md
• Contributing: CONTRIBUTING.md

Requirements

• Python >=3.9 (tested up to 3.14)
• Java (to run local LanguageTool server):
  • LanguageTool < 6.6: Java >=9
  • LanguageTool >= 6.6 (default): Java >=17

Installation

pip install --upgrade language_tool_python

Quick Start

Local server

import language_tool_python

with language_tool_python.LanguageTool("en-US") as tool:
    text = "A sentence with a error in the Hitchhiker's Guide tot he Galaxy"
    matches = tool.check(text)
    print(matches)
    print(tool.correct(text))

Public LanguageTool API

import language_tool_python

with language_tool_python.LanguageToolPublicAPI("es") as tool:
    matches = tool.check("Se a hecho un esfuerzo.")
    print(matches)

Your own remote LanguageTool server

import language_tool_python

with language_tool_python.LanguageTool(
    "en-US",
    remote_server="https://your-lt-server.example.com",
) as tool:
    print(tool.check("This are bad."))

Constructor Parameters Worth Knowing

language_tool_download_version (local server only)

Use this parameter to force which LanguageTool package is used when running a local server.

import language_tool_python

with language_tool_python.LanguageTool(
    "en-US",
    language_tool_download_version="6.7",
) as tool:
    print(tool.check("This are bad."))

Accepted formats:

• latest: latest snapshot available from the snapshot server
• YYYYMMDD: snapshot by date (example: 20260201)
• X.Y: release version (default: 6.8. Examples: 6.7, 4.0)

Notes:

• Only relevant when using a local server (no remote_server).
• Versions below 4.0 are not supported.

proxies (remote server only)

Use this parameter to pass proxy settings to requests when calling a remote LanguageTool server.

import language_tool_python

with language_tool_python.LanguageTool(
    "en-US",
    remote_server="https://your-lt-server.example.com",
    proxies={
        "http": "http://proxy.example.com:8080",
        "https": "http://proxy.example.com:8080",
    },
) as tool:
    print(tool.check("This are bad."))

Notes:

• proxies works only with remote_server.
• Passing proxies without remote_server raises ValueError.

Core Python API

Check text

matches = tool.check("This is noot okay.")

Each item is a Match object with these fields:

• rule_id
• message
• replacements
• offset_in_context, context, offset, error_length
• category, rule_issue_type
• sentence

Auto-correct

corrected = tool.correct("This is noot okay.")
# Uses first suggestion for each match

Apply only selected matches

text = "There is a bok on the table."
matches = tool.check(text)

# Keep a specific suggestion for first match
matches[0].select_replacement(2)

patched = language_tool_python.utils.correct(text, matches)

Check only parts matching a regex

matches = tool.check_matching_regions(
    'He said "I has a problem" but she replied "It are fine".',
    r'"[^"]*"',
)

Classify result quality

from language_tool_python.utils import classify_matches

status = classify_matches(tool.check("This is a cats."))
# TextStatus.CORRECT / TextStatus.FAULTY / TextStatus.GARBAGE

Rule and Language Controls

You can tune checks per instance:

tool.language = "en" # Can also be set from constructor (`LanguageTool("en")`)
tool.mother_tongue = "fr" # Can also be set from constructor (`LanguageTool("en", mother_tongue="fr")`)

tool.disabled_rules.update({"MORFOLOGIK_RULE_EN_US"})
tool.enabled_rules.update({"EN_A_VS_AN"})
tool.enabled_rules_only = False

tool.disabled_categories.update({"CASING"})
tool.enabled_categories.update({"GRAMMAR"})

tool.preferred_variants.update({"en-GB"})
tool.picky = True

Spellchecking control:

tool.disable_spellchecking()
tool.enable_spellchecking()

# Equivalent to:
tool.disabled_categories.update({"TYPOS"})
tool.disabled_categories.difference_update({"TYPOS"})

Custom Spellings

You can register domain-specific words:

with language_tool_python.LanguageTool(
    "en-US",
    new_spellings=["my_product_name", "my_team_term"],
    new_spellings_persist=False,
) as tool:
    print(tool.check("my_product_name is released"))

• new_spellings_persist=True (default): keeps words in the local LT spelling file.
• new_spellings_persist=False: session-only, words are removed on close().

Local Server Configuration (config=)

For local servers only, pass a config dictionary. Example:

with language_tool_python.LanguageTool(
    "en-US",
    config={
        "cacheSize": 1000,
        "pipelineCaching": True,
        "maxTextLength": 50000,
    },
) as tool:
    print(tool.check("Text to inspect"))

Supported keys:

• maxTextLength, maxTextHardLength, maxCheckTimeMillis
• maxErrorsPerWordRate, maxSpellingSuggestions, maxCheckThreads
• cacheSize, cacheTTLSeconds
• requestLimit, requestLimitInBytes, timeoutRequestLimit, requestLimitPeriodInSeconds
• languageModel, fasttextModel, fasttextBinary
• maxWorkQueueSize, rulesFile, blockedReferrers
• premiumOnly, disabledRuleIds
• pipelineCaching, maxPipelinePoolSize, pipelineExpireTimeInSeconds, pipelinePrewarming
• trustXForwardForHeader, suggestionsEnabled
• spellcheck-only language keys:
  • lang-<code>
  • lang-<code>-dictPath

Notes:

• remote_server and config cannot be used together.
• proxies can only be used with remote_server.

CLI

Entry point:

language_tool_python [OPTIONS] FILE [FILE ...]

Use - as file to read from stdin.

Examples:

# Check a file
language_tool_python -l en-US README.md

# Check stdin
echo "This are bad." | language_tool_python -l en-US -

# Auto-apply suggestions
language_tool_python -l en-US --apply input.txt

# Use only selected rules
language_tool_python -l en-US --enabled-only --enable MORFOLOGIK_RULE_EN_US input.txt

# Use remote LT server
language_tool_python -l en-US --remote-host 127.0.0.1 --remote-port 8081 input.txt

Main options:

• -l, --language CODE
• -m, --mother-tongue CODE
• -d, --disable RULES
• -e, --enable RULES
• --enabled-only
• -p, --picky
• -a, --apply
• -s, --spell-check-off
• --ignore-lines REGEX
• --remote-host HOST, --remote-port PORT
• -c, --encoding
• --verbose
• --version

Exit codes:

• 0: no issues
• 2: issues found

Environment Variables

• LTP_PATH: directory used to store downloaded LanguageTool packages.
  • default: ~/.cache/language_tool_python/
• LTP_JAR_DIR_PATH: use an existing local LanguageTool directory (skip download).
• LTP_DOWNLOAD_HOST_SNAPSHOT: override snapshot download host.
  • default: https://internal1.languagetool.org/snapshots/
• LTP_DOWNLOAD_HOST_RELEASE: override release download host.
  • default: https://languagetool.org/download/
• LTP_DOWNLOAD_HOST_ARCHIVE: override archive download host.
  • default: https://languagetool.org/download/archive/
• LTP_DOWNLOAD_SHA256_<VERSION>: version-specific expected SHA-256 for the downloaded LanguageTool archive, for example LTP_DOWNLOAD_SHA256_6_9_SNAPSHOT.
• LTP_DOWNLOAD_SHA256: fallback expected SHA-256 for the downloaded LanguageTool archive.
• LTP_BYPASS_VERIFIED_DOWNLOADS: set to true to skip SHA-256 verification.
• LTP_MAX_DOWNLOAD_BYTES: maximum downloaded ZIP size in bytes.
  • default: 536870912 (512 MiB)
• LTP_SAFE_ZIP_MAX_ARCHIVE_BYTES: maximum total compressed member size in bytes.
  • default: 536870912 (512 MiB)
• LTP_SAFE_ZIP_MAX_EXTRACTED_BYTES: maximum total extracted size in bytes.
  • default: 805306368 (768 MiB)
• LTP_SAFE_ZIP_MAX_MEMBERS: maximum ZIP member count.
  • default: 5000
• LTP_SAFE_ZIP_MAX_MEMBER_EXTRACTED_BYTES: maximum extracted size for a single ZIP member in bytes.
  • default: 134217728 (128 MiB)
• LTP_SAFE_ZIP_MAX_MEMBER_COMPRESSION_RATIO: maximum compression ratio for a single ZIP member.
  • default: 100.0
• LTP_SAFE_ZIP_MAX_TOTAL_COMPRESSION_RATIO: maximum compression ratio for the whole ZIP archive.
  • default: 10.0

Downloaded zips are verified with SHA-256 when a checksum is available. Checksums are resolved in this order:

1. LTP_DOWNLOAD_SHA256_<VERSION>, where non-alphanumeric characters in the version are replaced with _ and the name is uppercased.
2. LTP_DOWNLOAD_SHA256.
3. The bundled language_tool_python/integrity.toml manifest.

The bundled manifest covers release/archive downloads. Snapshots are not stable, so provide LTP_DOWNLOAD_SHA256_<VERSION> or LTP_DOWNLOAD_SHA256 if you want to verify a snapshot. If no checksum is available, the download proceeds without SHA-256 verification.

Example:

export LTP_PATH=/path/to/cache
export LTP_JAR_DIR_PATH=/path/to/LanguageTool-6.8
export LTP_DOWNLOAD_SHA256_6_8=<sha256>
# export LTP_BYPASS_VERIFIED_DOWNLOADS=true

Resource Management

When using a local server, prefer a context manager or explicit close():

with language_tool_python.LanguageTool("en-US") as tool:
    ...

# or
tool = language_tool_python.LanguageTool("en-US")
...
tool.close()

Client/Server Pattern

You can run LT on one process/host and connect from another client:

# Server side
server_tool = language_tool_python.LanguageTool("en-US")

# Client side
client_tool = language_tool_python.LanguageTool(
    "en-US",
    remote_server=f"http://127.0.0.1:{server_tool.port}",
)

Error Types

Main exceptions in language_tool_python.exceptions:

• LanguageToolError
  • ServerError
  • JavaError
  • PathError
  • RateLimitError

Development

# Install dev dependencies
uv sync --group tests --group docs --group types

# Lint / format / types
uvx ruff@0.15.12 check .
uvx ruff@0.15.12 format .
uvx mypy@2.0.0

# Tests
pytest

License

GPL-3.0-only. See LICENSE.

Acknowledgements

This project is based on the original language-check project: https://github.com/myint/language-check/