Is it safe to convert XLS to XLSX online?

Yes! Convert999 processes all files directly in your browser. Your files are never uploaded to any server, ensuring complete privacy and security.

How long does it take to convert XLS to XLSX?

Conversion is nearly instant for most files. Large files may take a few seconds depending on your device's processing power.

Is there a file size limit?

Convert999 supports files up to 2GB. Processing happens locally, so larger files depend on your device's available memory.

Do I need to install any software?

No installation required. Convert999 works entirely in your web browser on any device.

Free · No Upload · Instant

Converti XLS in XLSX Online — Gratis e Veloce

Convertitore online gratuito da XLS a XLSX. Converti i tuoi file Microsoft Excel 97-2003 in formato Microsoft Excel istantaneamente.

Scegli File

o trascina e rilascia i file qui

Dimensione max: 2GB

I tuoi file vengono elaborati localmente nel browser. Nulla viene caricato su alcun server.

Come Convertire XLS in XLSX

Carica il tuo file XLS cliccando "Scegli File" o trascinando.

Seleziona XLSX come formato di output.

Clicca "Converti Ora" e scarica il file convertito.

Info sul Formato XLS

Extension: .xls
Full name: Microsoft Excel 97-2003

Info sul Formato XLSX

Extension: .xlsx
Full name: Microsoft Excel

Domande Frequenti

È sicuro convertire XLS in XLSX online?

Sì! Convert999 elabora tutti i file direttamente nel tuo browser.

Quanto tempo ci vuole per convertire XLS in XLSX?

La conversione è quasi istantanea per la maggior parte dei file.

C'è un limite di dimensione del file?

Convert999 supporta file fino a 2GB.

Devo installare un software?

Nessuna installazione necessaria.

Can I convert XLS to XLSX on my phone?

Yes! Convert999 works on any device with a web browser — iPhone, Android, iPad, or desktop. No app installation required. Simply open the converter, upload your XLS file, and download the converted XLSX file.

Will I lose quality converting XLS to XLSX?

Convert999 uses high-quality conversion algorithms to minimize quality loss. For lossless formats, the conversion is exact. For lossy formats like images and audio, we use optimized settings that balance quality and file size.

Can I batch convert multiple XLS files to XLSX?

Yes, Convert999 supports batch conversion. Select or drag & drop multiple XLS files and convert them all to XLSX format at once. Each file is processed locally in your browser.

What is the difference between XLS and XLSX?

Microsoft Excel 97-2003 (XLS) and Microsoft Excel (XLSX) differ in compression, compatibility, and features. XLS is optimized for its native use cases, while XLSX may offer different advantages. Visit our XLS vs XLSX comparison page for a detailed breakdown.

Why Convert XLS to XLSX?

Advantages

✓Microsoft Excel offers better compatibility with modern applications and workflows
✓Converting is completely free with no file size limits on Convert999
✓Your files never leave your device — 100% private and secure conversion
✓Instant conversion without waiting for server processing

Key Differences

→XLS (Microsoft Excel 97-2003) is optimized for its native use cases
→XLSX (Microsoft Excel) may offer different compression or feature set
→Choose based on your target platform, quality needs, and file size requirements

Conversioni Correlate

XLSXLSX XLSODS XLSCSV XLSTSV XLSNUMBERS XLSXLSM XLSXLSX ODSXLSX CSVXLSX TSVXLSX NUMBERSXLSX XLSMXLSX

Explore More

.xls

XLS Converter

All XLS conversions

.xlsx

XLSX Converter

All XLSX conversions

XLS vs XLSX

Compare formats

Convert to XLSX

All sources → XLSX