CSV to Excel Converter — Convert CSV to XLSX Online
Private, secure online CSV to Excel converter with delimiter auto-detection and DDE formula protection.
- Runs in your browser
- Free, no signup
Drop your CSV or delimited text file here
or
Instant, private conversion to Microsoft Excel (.xlsx). Auto-detects delimiters. 100% processed on your device.
=, +, -, or @ are safely escaped as literal text cells so they cannot execute arbitrary formulas or system commands when opened in Microsoft Excel.
Table Preview
CSV data is parsed and assembled into an Excel workbook entirely inside your browser. No files or cell contents are transmitted over the network.
Comma-Separated Values (CSV) files are the standard output for database exports, analytics logs, and API payloads, but non-technical stakeholders and business analysts require rich, formatted Microsoft Excel (.xlsx) spreadsheets.
This tool converts CSV, TSV, and delimited text files into modern Office Open XML (.xlsx) workbooks. It automatically detects separators (commas, semicolons, tabs, and pipes), handles quoted fields containing embedded line breaks, preserves leading zeros for identifiers, and incorporates built-in protection against CSV formula injection attacks.
How to use this tool
- Upload your CSV, TSV, or TXT file by dragging it into the drop zone or clicking Browse.
- The converter automatically detects your file's delimiter and displays an interactive table preview.
- Configure your desired worksheet tab name, header row setting, and cell data type mode.
- Click "Convert & Download Excel (.xlsx)" to save your spreadsheet.
Spreadsheet Security & CSV Formula Injection Protection
CSV Formula Injection (also known as Formula Injection or DDE attacks) occurs when untrusted data contains characters such as =, +, -, or @ at the beginning of a cell. When imported into Microsoft Excel, Excel may automatically execute these cells as formulas or initiate external system commands.
ToolDuck includes automated formula injection protection enabled by default. Dangerous formula prefixes are safely neutralized with a single quote prefix, guaranteeing that Excel treats the values as literal text rather than executable formulas.
Preserving Leading Zeros & Formatting Numbers as Text
When opening raw CSV files directly in spreadsheet software, identifiers with leading zeros (e.g. employee IDs like "00123", postal codes, or phone numbers like "0987654321") are frequently truncated into plain integers like 123, permanently losing data.
By choosing the Explicit Text data type mode, ToolDuck tags cell values as text strings, preventing Excel from stripping leading zeros or converting long numbers into scientific notation.
Frequently asked questions
How does delimiter auto-detection work?
The engine samples lines across your file and computes frequency and consistency metrics for commas, semicolons, tabs, and pipes outside of quoted strings. You can also manually override the delimiter if desired.
Can this converter handle CSVs with commas and newlines inside quotes?
Yes. The parser strictly adheres to the RFC 4180 standard, ensuring multi-line cells and escaped double quotes ("") are preserved accurately.
Are my CSV files uploaded to any server?
No. All conversion logic runs locally in your web browser. No data, files, or row values are transmitted to ToolDuck or third parties.
Will my leading zeros be preserved in the generated Excel file?
Yes. By default, cells are exported as explicit text data types, ensuring values like "007" or "012345" remain intact.