xlsx-fixer 1.2.0

Fix Mac Excel corruption in openpyxl-generated .xlsx files

xlsx-fixer

A zero-dependency delivery-assurance layer for Python data pipelines.

Stop delivering "corrupted" Excel files to your clients and executives.

🚨 The 17-Year-Old Bug

If you generate .xlsx files with Python's openpyxl library and open them on a Mac, your stakeholders will see this terrifying warning:

⚠️ "We found a problem with some content in 'report.xlsx'. Do you want us to try to recover as much as we can?"

For a solo developer, this is annoying. For a data engineering team delivering automated reporting to C-suite executives or high-value clients, this completely destroys the professional credibility of the automation pipeline.

Why does this happen?

openpyxl hardcodes inline strings (t="inlineStr") for every text cell. Mac Excel's strict OOXML parser rejects this. The openpyxl maintainer has declined to fix this for 17+ years, calling it a permanent design decision.

How we fix it

xlsx-fixer intercepts the generated file, safely rebuilds the XML to use a proper shared string table (xl/sharedStrings.xml), drops inconsistent calculation states, and strips illegal control characters. One function call. Zero dependencies.

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🛠️ The Open Source Tier (Free)

This repository contains the core fix() engine. It is perfect for ad-hoc scripts and individual files.

pip install xlsx-fixer

Usage (Python)

from openpyxl import Workbook
from xlsx_fixer import fix

wb = Workbook()
ws = wb.active
ws["A1"] = "Hello, Mac Excel!"

# 1. Save normally
wb.save("report.xlsx")

# 2. Fix it before sending to the client
fix("report.xlsx") 

Usage (CLI)

# Fix a single file in-place
xlsx-fixer fix report.xlsx

# Check a file for corruption patterns without modifying
xlsx-fixer check report.xlsx

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🚀 The Enterprise Tier (xlsx-fixer Pro)

For data engineering teams and CI/CD pipelines, we offer xlsx-fixer Pro.

If you are running Airflow, GitHub Actions, or processing hundreds of files, the Open Source version is too slow and requires too much manual code modification. xlsx-fixer Pro is a pre-compiled, un-hackable binary (Linux/Mac/Windows) designed for enterprise scale.

Feature	xlsx-fixer (Free)	xlsx-fixer Pro
Single File Fix (fix())	✅	✅
Drop-in Patch (patch_openpyxl())	❌	✅
Multithreaded Batch CLI (batch)	❌	✅
Big Data Safe Mode (OOM prevention)	❌	✅
CI Audit Reporting (--report json)	❌	✅
Deployment Format	Source Code	Compiled Native Binary

⚡ The Drop-In Patch

Don't rewrite 100 legacy scripts. Just call patch_openpyxl() once at the top of your application, and every wb.save() call is automatically fixed in-place before it hits the disk.

💼 Commercial Licenses

License	Target Audience	Link
Pipeline License ($299/yr)	Solo Automators / Boutique Agencies	Purchase on Lemon Squeezy
Site License ($899/yr)	Enterprise Data Teams (Uncapped)	Purchase on Lemon Squeezy

Upon purchase, you will immediately receive your License Key and a secure download link for the compiled CI binaries.

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🔬 What It Fixes Under The Hood

#	Issue	Root Cause	Impact
1	Inline strings	openpyxl hardcodes t="inlineStr"	"We found a problem" dialog on every Mac open
2	fullCalcOnLoad	openpyxl sets fullCalcOnLoad="1" without generating calcChain.xml	Recovery dialog; formulas show 0
3	Stale calcChain.xml	References cells that no longer contain formulas	"Removed Records: Formula" in repair log
4	Control characters	Illegal XML 1.0 chars (U+0000-U+0008, etc.) in cell values	ST_Xstring validation failures

License

The free xlsx-fixer engine is licensed under the MIT License. See LICENSE for details.