CSV UTF-8 BOM for Excel: How to Keep Characters Readable

Sometimes a CSV is already saved correctly as UTF-8, but Excel still opens names such as José as José.

In that case, the file may not need to be repaired. Excel may simply need a small UTF-8 marker at the start of the CSV so it knows how to read the text.

That marker is called a UTF-8 BOM. This guide is about preventing Excel from misreading a correct UTF-8 CSV. If the file itself already contains broken text, use the CSV encoding repair guide first.

What is a UTF-8 BOM in plain language?

A UTF-8 BOM is a small marker placed at the start of a text file.

You do not see it as part of the spreadsheet. Its job is to tell programs such as Excel, "Read this file as UTF-8."

Modern software often reads UTF-8 correctly without the marker. Some Excel workflows are more reliable when the marker is present, especially when the file contains accented or non-English characters.

When should you use it?

Use a UTF-8 BOM when:

• the CSV is already UTF-8,
• the file looks correct in another app,
• Excel shows strange characters when you open the CSV,
• the recipient is likely to open the file directly in Excel.

You may want to leave it off when another system specifically asks for UTF-8 without a BOM.

How to export a CSV for Excel

1. 01

   Add the CSV

   Choose one CSV up to 300 MB from your device.

2. 02

   Choose CSV output

   This guide is about the CSV option. The UTF-8 BOM setting applies to CSV output.

3. 03

   Leave Add a UTF-8 BOM on

   It is enabled by default. Keep it on when the file will be opened in Excel and you want Excel to recognize UTF-8 reliably.

4. 04

   Export the file

   The tool creates a new Excel-friendly CSV while keeping your original values intact.

5. 05

   Open the result in Excel

   Check a few names, cities, and other values that contain accented or non-English characters before sending the file.

What happens to your file?

The CSV stays on your device while the export runs. It is not uploaded to our servers.

The tool creates a new UTF-8 CSV and, by default, adds the small marker Excel can use to recognize the file correctly.

The marker does not change your visible values. It only helps the receiving program decide how to read the text.

Practical limits

CSV output accepts one file up to 300 MB.

The cap follows the same registry method: the displayed limit comes from the shipped tool registry and is backed by first-party browser measurement. The first-party measurement evidence is recorded in docs/tool-audit/batch-a.md.

The same tool can also create an XLSX file, with a lower input limit shown on the Excel-safe CSV tool page. You do not need XLSX just to use the UTF-8 BOM; the BOM setting is for CSV output.

Adding a BOM cannot repair text that is already wrong inside the source file. If José is already stored in the CSV, use the encoding repair tool or export a fresh copy from the source system.

Some systems prefer UTF-8 without a BOM. If a website, database, or business system gives you exact CSV import requirements, follow those requirements instead of leaving the option on automatically.

Simple example

An English-language contact export can still contain characters that expose a bad encoding choice, for example Zoë O'Connor or Renée Smith. The BOM question is about how Excel identifies the file's UTF-8 encoding, not about which language the column labels use.

A correct UTF-8 CSV contains:

José

Excel may open it as:

José

After exporting the same UTF-8 text with the BOM enabled, Excel should show:

José

Export an Excel-friendly CSV

See the transformation

A dangerous formula becomes text while 00123 stays 00123

Make spreadsheet formulas harmless while preserving identifiers such as 00123 exactly as text.

Input

=SUM(A2:A9)

00123

1234567890123456

Result

'=SUM(A2:A9)

00123

1234567890123456