What is the DIF file format?
.dif is a spreadsheet data interchange format that stores data in plain text. The format is standardized, meaning that exporting data to a .dif file preserves the data layout and can be directly imported to other spreadsheet programs. Many parsing issues - such as the wrong field-separator problem when importing data from CSV files - are eliminated with this approach.
A single .dif file can hold only a single spreadsheet table; multiple .dif files can be used together when exchanging data across sheets. The format allows data from various applications to be shared with different spreadsheet programs in a formatting-agnostic way. Unlike XLSX workbooks or ODS files, .dif carries no formatting, fonts, charts, macros, or formulas - only the calculated cell values of one flat table.
The .dif standard was developed by Software Arts in 1981 for the VisiCalc spreadsheet, and was later adopted as an open de facto interchange format by many applications. A .dif file always begins with the literal keyword TABLE on its own line, followed by a version line 0,1 and VECTORS (column count), TUPLES (row count), and a DATA section that lists each cell as a type code and value pair. Note that .dif should not be confused with a Unix diff/patch file, which can share the same extension.
Security & safety
RISK: LOWA DIF spreadsheet is plain text with no macros, scripts or embedded objects, so opening one is low-risk - there is no formula or macro engine inside the file itself. As with any data file, only the values are present; the usual caution is making sure a file labelled .dif is actually the spreadsheet format and not something else (e.g. a diff/patch text file) before importing it. Avoid obscure "DIF opener" download sites - Excel, LibreOffice Calc and Google Sheets already read DIF.
Format details
in a nutshell- diff / patch file (Unix) - A .dif (or .diff) can be a text patch produced by the 'diff' tool listing line changes between files - unrelated to the spreadsheet format.
- AVHRR / satellite imagery DIF - Some remote-sensing toolchains use .dif for data products; a niche meaning distinct from the spreadsheet interchange format.
Programs that open DIF files
Windows4 apps
Microsoft Excel
Paid File -> Open the .dif (choose 'All Files' if needed); it loads as a grid. Save As -> XLSX/CSV to keep it in a modern format. 
NotePad++ text editor
Open-source Open the .dif as text to inspect the raw TABLE/VECTORS/TUPLES structure (viewing only). 
Gnumeric
Open-source Open the .dif in this lightweight spreadsheet (good DIF/legacy-format support). 
LibreOffice Calc
Open-source Open the .dif directly (free); Calc imports DIF and lets you Save As ODS/XLSX/CSV. 
macOS2 apps
Microsoft Excel
Paid File -> Open the .dif; it imports as a sheet. Save As XLSX/CSV for a modern copy. 
Linux2 apps
Gnumeric
Open-source Lightweight spreadsheet with solid legacy-format support; opens .dif and saves CSV/XLSX.
LibreOffice Calc
Open-source Open the .dif directly; the standard free spreadsheet on Linux, with DIF import/export. 
Google Sheets
Free File -> Import -> Upload the .dif; Sheets parses it into a grid, then File -> Download as XLSX/CSV. Technical details
deep spec| File encoding | Plain ASCII text (7-bit); no binary content or Unicode |
| File structure | Three sections in order: header keywords TABLE, VECTORS, TUPLES - each followed by a numeric line and a quoted comment - then a DATA section listing every cell |
| Magic bytes / identification | No binary signature; file always begins with the literal token TABLE on its own line, then the version line 0,1 |
| MIME type | text/plain (also application/x-dif or application/dif) |
| VECTORS field | Header keyword declaring the number of columns (vectors) in the table |
| TUPLES field | Header keyword declaring the number of rows (tuples) in the table |
| Cell data types | Numeric values (type 0) and string literals (type 1); formulas are not stored - only their computed results |
| Sheets per file | One flat two-dimensional table only; multi-sheet workbooks require separate .dif files |
| Formatting support | None - no fonts, colors, column widths, borders, charts, or macros are stored |
| Compression | None - stored as uncompressed plain text |
| Encryption | None - no built-in security or password protection |
| Typical file size | A few KB to a few hundred KB for a single table of values |
| Superseded by | CSV for plain tabular values; XLSX and ODS for full-featured workbook exchange |
| Name collision | Extension .dif is also used by Unix diff/patch output files - entirely unrelated to the spreadsheet format |
| Released | 1981 (created by Software Arts for VisiCalc to exchange single-sheet data) |
| Latest version | Stable since the early 1980s - the format has not evolved |
| Open standard | Yes · royalty-free |
| Specification | en.wikipedia.org |
DIF conversions
Community Q&A
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