XLS: Legacy Excel Spreadsheet
The foundation of digital spreadsheets.
Learn about the binary format that defined business data analysis before the age of open standards.
What is an
.xls
File?
It is the old way Microsoft Excel saved spreadsheets. Even though it is old, you will still find it in many workplaces today. Here is everything you need to know about it.
The Basics
Think of a spreadsheet like a giant piece of digital graph paper. It is made of boxes. You can put numbers, text, or math rules into these boxes.
For almost 20 years, when people saved these digital graph papers on a computer, the file name ended with .xls.
- Holds numbers and text
- Can do automatic math
- Can make charts and graphs
Inside the File
1. Worksheets
One file can hold many pages. Each page is called a Worksheet. You switch between them using tabs at the bottom.
2. Cells
The tiny boxes on the page. Every piece of data lives inside a cell. They have names like A1 or B5.
3. Formulas
Math rules. You can tell a cell to add up the numbers in other cells. If you change a number, the total updates instantly.
A Quick History
1987
The Beginning
Microsoft creates Excel for Windows. It uses the .xls format to save files. It becomes the standard for businesses everywhere.
1997 - 2003
The Golden Era
Every office uses it. Financial reports, school lists, and store inventory are all saved as .xls files.
2007
The Big Change
Microsoft invents a better, safer format called .xlsx. The old .xls is no longer the default choice.
Today
Still Alive
Even though it is old, millions of .xls files still exist in company archives and government databases.
The Old vs. The New
If the old format worked, why did they change it? The answer is size and safety. Here is a simple look at the difference.
.xls
THE OLD WAY- Files are very large. They take up a lot of space on your computer.
- Easier for bad code (viruses) to hide inside them.
- Can hold up to 65,536 rows of data.
.xlsx
THE NEW WAY- Files are zipped tight. They are very small and save space.
- Much safer. Harder for viruses to hide inside.
- Can hold over 1,000,000 rows of data.
Why are they still around?
Old Company Records
01A company that has been doing business since 1995 has decades of financial reports saved as .xls files. Nobody has had the time to convert thousands of old files.
Old Software Programs
02Some businesses use very old software machines, like cash registers or old factory tools. These machines can only export data in the old .xls format.
Government Data
03Many public records and city databases were built a long time ago. When you download public data today, it still often comes as an .xls file.
Shared by Mistake
04Sometimes, people using modern Excel click "Save As" and accidentally pick the old format from the list without realizing it.
How to open them today
Do not worry if someone emails you an .xls file. You do not need a computer from 2003 to read it. Modern tools can easily read the old files.
Be Careful with Old Files
Because the .xls format is old, it does not have modern security.
The Danger: Macros
Macros are little pieces of code hidden inside a spreadsheet to automate tasks. Bad people can write bad code (viruses) and hide it in an .xls file. If you download an .xls file from the internet or from someone you do not know, do not click "Enable Macros" when you open it.
How to Update Your Files
If you have an .xls file, you should convert it to the new .xlsx format. It is very easy and takes ten seconds.
Open the File
Double-click your .xls file to open it in a modern program like Excel or Google Sheets.
Click "Save As"
Go to the File menu at the top left corner of the screen and click the "Save As" or "Download As" button.
Pick .xlsx
In the dropdown menu, choose Excel Workbook (*.xlsx) and click save. You are done!
The "Compatibility Mode" Warning
When you open an `.xls` file in modern Excel, you will see a banner at the top that says "Compatibility Mode". Do not panic. This just means Excel is turning off its newest features so it does not accidentally break your old file.
The Hard Limit
Imagine a tower of boxes. An `.xls` file can only go 65,536 boxes high. If you try to paste 100,000 rows of data into it, the bottom 34,464 rows will just vanish. No warning. They will just be gone.
What You Lose
If you use a modern Excel feature and then save the file as an old `.xls`, these things will break or disappear completely:
Sparklines
Mini charts inside a single cell will vanish.
New Math Rules
New formulas like XLOOKUP will turn into broken errors.
Co-Authoring
You cannot edit the file at the same time as your team.
Can I open it on my phone?
Yes. Both iPhones and Androids can open `.xls` files.
If someone sends you one in an email, you can tap it. The free Microsoft Excel app or Google Sheets app will open it. However, because spreadsheets are huge grids, it is very hard to read tiny boxes on a small screen. You will have to zoom in a lot.
Weak Passwords
In the past, people put passwords on their `.xls` files to keep secrets safe.
Do not trust these old locks today.
The lock on an `.xls` file is very weak by today's standards. A normal computer today can guess the password and break into an old `.xls` file in a few minutes. If you have a secret file, you must convert it to `.xlsx` which has a much stronger modern lock.
Printing Nightmares
Older spreadsheets were famous for wasting paper. Because a spreadsheet is a giant grid, printers get confused.
If your table was just a little bit too wide for a standard piece of paper, the computer would print that one extra column on 50 blank pages. Always click "Print Preview" before printing an old file, or you might empty your printer's paper tray.
COMMON ERROR:
"The file format and extension of 'report.xls' don't match."
Why this happens: Sometimes, people try to convert a new file into an old file just by clicking rename and typing `.xls` at the end of the name. This does not work. It confuses the computer.
The Fix: Never rename the file extension yourself. Always open the file and click "Save As" to let the software do the work.
File Corruption (When Files Break)
Old `.xls` files break more easily than new ones. If your computer crashes or loses power while it is saving an `.xls` file, the whole file might be ruined forever. The new `.xlsx` format is built to fix itself if a crash happens. This is another big reason to upgrade your files.
Are .xls files legal records?
Yes. Many courts, lawyers, and government tax offices still accept `.xls` files as official evidence. Because they are old, they perfectly show exactly what a business was doing many years ago. Do not delete them if they are official records.
Old Words You Might Hear
Workbook
Just another word for the entire Excel file itself.
Macro
A recorded set of clicks and math that runs automatically.
Lotus 1-2-3
A very old software that came before Excel. Excel killed it.
CSV
A simpler file that only holds raw text. No colors, no math rules.
The Golden Rules of .xls
More in this series
Master more skills with other tutorials from the Spreadsheets series.
Data Engineering
- DB: Generic Database File: The universal data container.
- SQLite: Portable Database: A database in a single file.
- SQL: Structured Query Language: The language of data.
- CSV: Comma-Separated Values: The universal data exchange format.
Spreadsheets
- NUMBERS: Apple Numbers Spreadsheet: Visual data storytelling.
- XLSM: Macro-Enabled Spreadsheet: Excel with automation power.
- ODS: OpenDocument Spreadsheet: The open spreadsheet standard.
- XLS: Legacy Excel Spreadsheet: The foundation of digital spreadsheets.
- XLSX: Modern Excel Spreadsheet: The data powerhouse.
Presentations
- ODP: OpenDocument Presentation: The open standard for slides.
- PPT: Legacy Presentation: The classic slide deck format.
- PPTX: Modern Presentation: The gold standard for slide decks.
Word Processing
- WPS: WPS Office Document: The lightweight contender.
- PAGES: Apple Pages Document: The designer's word processor.
- ODT: OpenDocument Text: The open text standard.
- DOC: Legacy Word Document: The classic document format.
- DOCX: Modern Word Document: The standard for office documents.
- RTF: Rich Text Format: The universal translator.
Digital Publishing
- TEX: LaTeX Document: The mathematician's choice.
- PDF: Portable Document Format: The digital paper standard.
Software Engineering
- TSX: TypeScript XML: The modern web component.
Markdown & Text
- MD: Markdown: The programmer's writer.
- TXT: Plain Text: The simplest file in the world.