XLSX Won't Open? Convert to XLS Instantly
Fast, instant XLSX to XLS conversion. No signup required. Just drop your .xlsx file and get .xls in seconds.
Batch Settings
Some metadata may not survive
Your XLSX file may contain Office XML properties metadata. XLS has limited or no support for these metadata types. Location data (GPS), camera settings, and color profiles may be stripped during conversion.
Certains logiciels ne lâchent pas le passé facilement. Entre les administrations qui tournent encore sous Excel 2003, les cabinets d'expertise comptable attachés à leurs macros d'époque et les universités dont les serveurs refusent obstinément tout fichier .xlsx, le besoin de revenir au bon vieux format .xls reste bien réel. Convertir un classeur moderne vers ce format ancien n'a rien d'un recul — c'est simplement s'adapter à des contraintes concrètes, sans perdre de temps à chercher une vieille version d'Office ou à bricoler des paramètres d'enregistrement. Notre outil s'en charge en quelques secondes, sans installation, sans compte à créer.
- Dossiers de subvention pour les collectivités territoriales françaises exigeant des pièces jointes en .xls
- Fichiers de notes transmis aux secrétariats pédagogiques des universités québécoises sous logiciels hérités
- Grilles tarifaires envoyées à des imprimeurs ou façonniers belges dont l'ERP n'accepte pas l'xlsx
En Suisse romande, plusieurs cantons maintiennent des systèmes de gestion documentaire standardisés sur d'anciennes versions d'Office, rendant le format .xls obligatoire pour certains formulaires officiels. Il n'est pas rare que des prestataires externes se heurtent à ce prérequis sans avertissement préalable.
About XLSX to XLS Conversion
Dealing with a XLSX file that won't open on your device? You're not alone — XLSX compatibility issues are one of the most common reasons people search for a file converter. XLSX is Microsoft Excel's modern format supporting formulas, charts, and multiple sheets.
The fix is simple: convert your XLSX to XLS. XLS is the legacy Excel format (pre-2007) — still encountered in business workflows. This conversion lets you convert between formats quickly, solving the problem in seconds rather than hours of troubleshooting.
Full Name: XLSX uses Microsoft Excel Spreadsheet, while XLS uses Microsoft Excel Legacy. Compression: XLSX uses Lossless, while XLS uses None (uncompressed). Typical File Size: XLSX uses 50 KB–50 MB, while XLS uses 50 KB–50 MB. Converting XLSX to XLS maintains high quality with CocoConvert's optimised encoder settings.
CocoConvert processes your XLSX file on secure servers in Germany — upload, convert, download. Your files are encrypted via TLS and automatically deleted within 24 hours. No account needed, no software to install, and it works on any device with a browser.
This conversion is ideal when you You need maximum device and software compatibility. Common misconception: ""XLS will be smaller than my XLSX file"" — in reality, xls uses no compression, so the output file is often larger than a lossy xlsx. if you need a small file, xls may not be the right choice.
The conversion engine behind CocoConvert uses FFmpeg, Sharp, and qpdf — the same open-source libraries trusted by Netflix, YouTube, and enterprise platforms. Pro users can batch convert up to 100 files at once.
How to Convert XLSX to XLS
- 1
Add your XLSX file
Drag and drop your .xlsx file into the converter, or tap "Browse" to pick it from your device. Multiple files are supported for batch processing.
- 2
Pick XLS output
Select .xls as the target format. CocoConvert automatically applies the best quality settings for this conversion.
- 3
Start conversion
Hit the Convert button. The spreadsheet engine processes your file server-side — no CPU drain on your device.
- 4
Save your file
Once done, download your .xls file. For batch jobs, download all at once as a zip.
What Happens When You Convert XLSX to XLS
Your XLSX file is decoded and re-encoded as XLS.
Your XLSX file is uploaded and the format is validated
The file content is decoded into its raw representation
The data is re-encoded in XLS format with optimal settings
The converted file is ready for download
XLSX vs XLS — Detailed Comparison
| Feature | .XLSX | .XLS |
|---|---|---|
| Full Name | Microsoft Excel Spreadsheet | Microsoft Excel Legacy |
| Compression | Lossless | None (uncompressed) |
| Typical File Size | 50 KB–50 MB | 50 KB–50 MB |
| Platform Support | Universal | Universal |
| Browser Support | none | none |
| Year Created | 2006 | 1987 |
| Open Standard | Yes | No |
Should You Convert XLSX to XLS?
When to Convert
- ✓You need maximum device and software compatibility
Common Mistakes When Converting XLSX to XLS
"XLS will be smaller than my XLSX file"
XLS uses no compression, so the output file is often larger than a lossy XLSX. If you need a small file, XLS may not be the right choice.
Frequently Asked Questions
Why won't my XLSX file open?
XLSX files may not open if your device lacks the right codec or application. Converting to XLS — a more widely supported format — usually resolves this. XLS is the legacy Excel format (pre-2007) — still encountered in business workflows.
Is it safe to convert XLSX to XLS online?
Yes. CocoConvert encrypts your file via TLS, processes it on isolated servers in Germany, and permanently deletes it within 24 hours. Your files are never shared or analysed.
Will I lose quality converting XLSX to XLS?
Converting XLSX to XLS maintains high quality with CocoConvert's optimised encoder settings. CocoConvert uses high-quality encoder defaults to preserve as much fidelity as possible.
How large can my XLSX file be?
Free users can convert files up to 250 MB each. Pro users get a 5 GB limit per file, and Business API users have custom limits.
Can I convert XLSX to XLS on my phone?
Absolutely. CocoConvert works in any modern browser — iOS Safari, Android Chrome, and all desktop browsers. No app required.
Versions are pinned in our worker Dockerfile and re-built via CI on every change.