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Fix CSV Encoding Issues in Excel: Detect, Diagnose, and Repair Garbled Text

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The purpose of this article is to explain how to detect CSV file encodings, understand why Excel sometimes corrupts characters when opening CSV files, and provide practical, repeatable workflows to remediate encoding issues and standardize clean imports.

1. Why CSV encoding breaks when opening files in Excel

CSV is a plain text format, and every text file is stored using a character encoding such as UTF-8, UTF-16, Windows-1252, Shift-JIS, or others. Excel does not store the encoding inside the CSV, so when you double-click a CSV file in Windows Explorer, Excel must guess which encoding to use. On many Windows systems, Excel historically assumes the system “ANSI” code page such as Windows-1252 for Western languages, which causes problems when the CSV is actually UTF-8 or another Unicode encoding.

Modern Excel versions provide safer import options through the Data tab and Power Query, but if users still double-click CSV files, garbled characters, question marks, or broken delimiters frequently appear. This is not a problem with the data itself. It is a mismatch between the encoding used when the CSV was written and the encoding Excel assumes when it is opened.

2. Typical symptoms of encoding problems in Excel

Before changing anything, confirm that a data quality issue is really caused by encoding. Common symptoms include the following patterns.

  • Accented characters (é, ñ, ü), currency symbols (€, £, ¥), or non-Latin scripts display as question marks, black diamonds, or random symbols.
  • Asian characters (Korean, Japanese, Chinese) appear as sequences of Latin letters, numbers, and punctuation instead of ideographs.
  • Column delimiters are misinterpreted so that entire rows appear in a single column or columns shift position unexpectedly.
  • Only some rows are corrupted, typically those containing special characters, while other rows remain readable.
  • The same CSV looks correct in a browser or text editor but appears broken only inside Excel.
Note : If the CSV displays correctly in a text editor but not in Excel, the file itself is usually valid. The issue is almost always Excel choosing the wrong encoding while opening the file.

3. How Excel interprets CSV encoding by default

Excel’s behavior depends on version and platform.

  • Excel on Windows when double-clicking CSV. Typically uses the system ANSI code page (for example Windows-1252 in many Western locales). This behavior often corrupts UTF-8 CSV files that do not include a Byte Order Mark (BOM).
  • Excel “Import text/CSV” command. When importing via the Data tab and “From Text/CSV”, Excel shows a preview and offers a File Origin or encoding list where you can choose UTF-8, UTF-16, or legacy encodings.
  • Power Query connectors. Power Query’s Text/CSV connector and the underlying Csv.Document function accept an explicit Encoding parameter, which by default is 65001 (UTF-8) in current documentation.

To prevent encoding issues, the goal is to stop relying on Excel’s implicit guesses and always use an import method where the encoding is chosen explicitly.

4. Detecting CSV encoding before opening in Excel

Excel cannot reliably auto-detect encoding for arbitrary CSV files. For robust workflows, treat encoding detection as a separate step, especially when you receive data from multiple systems.

4.1 Check encoding with a text editor

Many modern text editors display the detected encoding in the status bar or in a “Save with encoding” dialog. For example, editors such as VS Code, Notepad++, or similar tools often show UTF-8, UTF-8 with BOM, or Windows-1252 at the bottom of the window. Support articles for CSV import into web platforms commonly recommend opening the CSV in a text editor and confirming that it is UTF-8 before uploading or reusing the file.

Recommended manual workflow.

  1. Open the CSV in a capable text editor, not in Excel.
  2. Inspect the encoding shown in the status bar or file properties.
  3. If necessary, re-save the file as UTF-8 (preferably with BOM for legacy Excel compatibility) without changing delimiters.
  4. After confirming the encoding, import the CSV into Excel using the Data tab instead of double-clicking.

4.2 Use Python and chardet to infer encoding

For repeated or automated processes, encoding can be inferred programmatically. The chardet library for Python analyzes sample bytes and estimates the most likely encoding. Documentation and tutorials emphasize that chardet works well when enough non-ASCII characters are present and is widely used in data engineering pipelines.

Example Python helper script.

import chardet
def detect_encoding(path, sample_size=100_000):
with open(path, "rb") as f:
raw = f.read(sample_size)
result = chardet.detect(raw)
return result["encoding"], result["confidence"]

csv_path = r"C:\data\input.csv"
encoding, confidence = detect_encoding(csv_path)
print(f"Detected encoding: {encoding} (confidence {confidence:.2f})")

This is an estimate rather than a guarantee, but it is usually sufficient to choose a safe encoding when importing into Excel or Power Query.

4.3 Use PowerShell with explicit encodings

On Windows, PowerShell does not automatically determine encodings, but documentation and community discussions highlight that you can read a file multiple times with different encodings or specify the expected encoding directly, such as -Encoding UTF8 or -Encoding Default.

Example PowerShell snippet to test several encodings.

$path = "C:\data\input.csv"
Try UTF-8
$utf8 = Get-Content -Path $path -Encoding utf8
$utf8[0..5]

Try default ANSI code page
$ansi = Get-Content -Path $path -Encoding default
$ansi[0..5]

Try Unicode (UTF-16LE)
$utf16 = Get-Content -Path $path -Encoding unicode
$utf16[0..5]

Compare the outputs and choose the version where special characters display correctly. Use that encoding when importing into Excel.

5. Safely importing CSV into Excel with explicit encoding

Instead of opening CSV files by double-clicking, use controlled import workflows that let you choose encoding, delimiter, and data types.

5.1 Modern method: Data > From Text/CSV (Get & Transform)

Current Microsoft 365 documentation recommends importing text files through the Data tab to preserve data integrity and avoid implicit conversions.

  1. In Excel, open a new or existing workbook.
  2. Go to the Data tab.
  3. Select Get Data > From File > From Text/CSV (label varies slightly by version).
  4. Pick your CSV file and confirm.
  5. In the preview dialog, verify:
    • File Origin or Encoding set to the correct encoding (for example 65001: Unicode (UTF-8)).
    • Delimiter matches the file (comma, semicolon, tab, etc.).
    • Characters and column boundaries display correctly in the preview.
  6. Click Load to load directly or Transform Data to open Power Query for additional shaping.
Note : Train users to import CSV via the Data tab instead of double-clicking the file. This single change eliminates many encoding, delimiter, and data type issues.

5.2 Legacy Text Import Wizard workflow

Some Excel environments still rely on the Text Import Wizard, which also allows you to control encoding and delimiters.

  1. In Excel, go to Data.
  2. Select Get Data > Legacy Wizards > From Text (Legacy), or use the older From Text option if it is enabled.
  3. Choose the CSV file.
  4. In Step 1 of the wizard:
    • Set File origin to the correct encoding (for example UTF-8 or a specific code page) as recommended in user guides and expert answers.
    • Select Delimited unless you truly have fixed-width columns.
  5. In Step 2, choose the delimiter (comma, semicolon, tab) and confirm that the preview looks correct.
  6. In Step 3, optionally set column data formats (Text, Date, etc.) to avoid unwanted type changes.
  7. Finish and choose where to place the data in the workbook.

5.3 Power Query with explicit encoding in M code

When using Power Query, you can permanently fix the encoding at the query level so that refreshes always apply the same setting. The official Csv.Document documentation describes an Encoding option parameter that accepts numeric values such as 65001 for UTF-8.

Example M code.

let Source = Csv.Document( File.Contents("C:\data\input.csv"), [ Delimiter = ",", Encoding = 65001, // UTF-8 QuoteStyle = QuoteStyle.Csv ] ), #"Promoted Headers" = Table.PromoteHeaders(Source, [PromoteAllScalars = true]) in #"Promoted Headers"

Once this query is configured, subsequent refreshes will always treat the CSV as UTF-8, independent of user locale or Excel’s default assumptions.

6. Fixing a CSV that already opened incorrectly in Excel

Users often notice the problem only after opening the CSV, seeing corrupted characters, and sometimes saving the workbook. The recovery strategy depends on whether the original CSV is still available.

6.1 If the original CSV is still available

  1. Close the Excel workbook without saving if possible.
  2. Follow the detection steps to identify the correct encoding using a text editor or script.
  3. Reopen Excel and import the CSV via Data > From Text/CSV or the Text Import Wizard, explicitly setting the encoding.
  4. Verify key rows with special characters and ensure they match what you see in the text editor.

6.2 If the CSV was saved as XLSX after corruption

If a user has already saved the garbled data as an Excel workbook and the original CSV no longer exists, the underlying byte information has been lost. In such cases, spreadsheet formulas cannot reconstruct the original characters because Excel has already converted them to the wrong Unicode code points.

Note : The only reliable way to restore correct text after a bad import is to re-import from a clean source file. Implement retention policies or automated exports so that source CSV files are kept for troubleshooting instead of being overwritten immediately.

7. Standardizing CSV export and encoding in your data pipeline

Long term, the most effective strategy is to standardize on a small set of encodings and export options so that CSV files are consistently produced in formats that Excel can handle.

7.1 Exporting clean CSV from Excel

Recent Excel versions provide dedicated UTF-8 export formats. Support documentation and community posts frequently recommend exporting as CSV UTF-8 (Comma delimited) when sharing data with systems that expect Unicode text.

  1. Open the workbook in Excel.
  2. Click File > Save As.
  3. Select a folder.
  4. In Save as type, choose CSV UTF-8 (Comma delimited) (*.csv).
  5. Save the file and confirm any warnings about features not supported in CSV.

7.2 Exporting from other systems

When CSVs are generated by databases, SaaS platforms, or scripts, configure their export settings to use UTF-8 whenever possible. Many tools default to UTF-8 already. For legacy consumers that rely on Excel, consider enabling a BOM or using a code page that matches the prevalent Excel environment if UTF-8 is unavailable.

Key practices for system owners.

  • Document the encoding used for each export job and include it in technical specifications.
  • Provide a short “How to import this CSV into Excel” guide for end users, describing the correct import command and encoding selection.
  • Where practical, provide test files with special characters so that users can visually confirm that the import procedure is correct.

7.3 Organizational “encoding playbook”

For teams handling multi-language data, it is useful to maintain an internal playbook that describes which encodings are expected from each source and how to import them into Excel. An example structure is shown below.

Source system Region / language Expected encoding Excel import method Fallback / notes
CRM platform A Global, mixed languages UTF-8 Data > From Text/CSV, File Origin = UTF-8 Do not open by double-clicking CSV.
Legacy ERP B Western Europe Windows-1252 Legacy Text Import Wizard, File origin = Western European (Windows) Re-save as CSV UTF-8 before reusing externally.
Manufacturing system C East Asia UTF-8 with BOM Power Query, Encoding = 65001 Use reference test file with non-Latin characters.

8. Quick troubleshooting checklist for CSV encoding in Excel

The following checklist summarizes the detection and remediation steps for day-to-day support.

  1. Confirm symptom. Verify that the issue is limited to Excel and that the CSV looks correct in a text editor.
  2. Identify encoding. Use a text editor, Python + chardet, or a PowerShell script to infer the encoding.
  3. Use controlled import. In Excel, import via Data > From Text/CSV or the Text Import Wizard, explicitly setting the encoding and delimiter.
  4. Harden the pipeline. Standardize exports to UTF-8 or documented code pages and provide instructions to Excel users.
  5. Preserve originals. Keep original CSVs under version control so you can re-import them if an import procedure changes.

FAQ

Why does my UTF-8 CSV look fine in a text editor but not in Excel?

Most modern text editors default to UTF-8 and detect it even without a BOM. When you double-click a CSV in Windows, however, Excel often uses the system ANSI encoding instead of UTF-8. As a result, any non-ASCII characters become corrupted. The data is correct, but Excel is guessing the wrong encoding. Import the file via the Data tab and explicitly choose UTF-8 to resolve the problem.

Can Excel automatically detect CSV encoding?

Excel does not guarantee accurate automatic encoding detection for CSV files. In practice, it relies on heuristics and system defaults, which fail frequently for mixed-language or Unicode data. To avoid risk, treat encoding selection as a deliberate step and use import methods that let you specify File Origin or encoding directly.

Is there a formula I can use inside Excel to detect wrong encoding?

No Excel formula can recover the original bytes once text has been mis-decoded. Functions such as CODE, UNICODE, and LEN can help you identify abnormal patterns, but they cannot tell you which encoding should have been used. Detection should be done before import using scripts or external tools. If the CSV has already been imported incorrectly and the original file is unavailable, the corruption is usually irreversible.

What is the safest encoding for CSV files that must work across systems?

UTF-8 is widely considered the safest choice for cross-platform CSV exchange because it supports all Unicode characters and is supported by modern tools. When working with legacy Excel versions or workflows that still expect older encodings, UTF-8 with a BOM can improve compatibility, but your organization should standardize and document the expectations for each consumer system.

How can I prevent users from double-clicking CSV files and causing issues?

There is no universal technical block, but you can mitigate risk by training users, updating documentation, and providing standard import macros or Power Query templates. Many teams also adopt folder structures where CSV files are handled by automated processes rather than opened directly, and they distribute short “How to import this CSV” guides that emphasize using the Data tab instead of opening files from Explorer.

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