Common CSV Problems (and How to Fix Them)
A practical guide for developers, analysts and data-driven teams
CSV files are among the simplest and most universal ways to exchange structured data. They are lightweight, compatible with almost every system, and easy to generate. But despite their simplicity, CSV files often cause a surprising number of errors — from broken imports to corrupted characters or misaligned columns.
In this article, we break down the most common CSV problems and explain how to fix them quickly and reliably.
1. Wrong or inconsistent delimiters
CSV files don’t always use commas. Depending on region, software or export settings, delimiters may be:
,comma;semicolon\ttab|pipe
Typical symptoms:
- all values end up in a single column
- columns break incorrectly
- import tools fail to detect the correct structure
How to fix it
- Check the delimiter during export
- Specify the correct delimiter when importing
- Standardize one delimiter across your team or systems
- Use tools that auto-detect the delimiter reliably
2. Encoding issues (broken characters, “München”, �)
Encoding mismatches are one of the most common CSV headaches. Different systems use different encodings:
- UTF-8
- UTF-8 with BOM
- ISO-8859-1 / Latin-1
- Windows-1252
Signs of encoding errors:
- umlauts and accents turn into weird symbols
- emojis disappear
- special characters become
?or�
How to fix it
- Always export CSV files in UTF-8
- Select the correct encoding when importing
- Avoid mixing tools that use different defaults
- Validate the encoding before processing the file
3. Improper quoting or escaping
CSV files allow commas, semicolons, or even line breaks inside a field — but only if fields are wrapped in quotes. Incorrect quoting breaks the entire CSV.
Common problems:
- text containing commas splits into multiple columns
- quotes inside a field are not escaped
- multiline fields corrupt the structure
How to fix it
- Wrap text fields in double quotes (
"…") - Escape internal quotes with (
"") - Use tools that automatically handle escaping
- Avoid manual editing in Excel
4. Line breaks inside fields
Line breaks often appear in comments or descriptions. If they aren’t wrapped correctly, importers may interpret them as new rows.
How to fix it
- Surround multiline fields with quotes
- Ensure your export tool supports multiline values
- Validate CSVs before importing them into pipelines
5. Mixed line endings (LF, CRLF, CR)
Operating systems use different line-ending formats:
- Linux / UNIX →
LF - Windows →
CRLF - old macOS →
CR
Mixed line endings can cause:
- incorrect row counts
- failed imports
- scripts that stop midway
How to fix it
- Normalize line endings to
LF - Configure your editor or code formatter properly
- Clean up line endings before running scripts
6. Missing or inconsistent headers
Headers define the structure of the file. Problems arise when:
- no header row exists
- column names are duplicated
- columns are renamed inconsistently
- headers contain spaces or special characters
How to fix it
- Always include a clear header row
- Use consistent naming conventions
- Avoid spaces and special characters
- Document your CSV schema
7. Inconsistent data formats
Because CSV stores everything as text, systems may interpret data differently:
- dates (
01/02/2024) become ambiguous - number formats vary by region
- boolean values differ (
TRUE,true,1,"yes")
How to fix it
- Use ISO-8601 dates (
YYYY-MM-DD) - Use
.for decimal separators - Standardize boolean values
- Validate data types before importing
8. Large file size (performance issues)
Large CSV files (100MB+) often cause:
- Excel freezing or crashing
- scripts running out of memory
- slow imports
- browser-based tools failing completely
How to fix it
- Split large files into smaller chunks
- Process them using streaming (chunk-based) techniques
- Compress with Gzip
- Use tools optimized for large datasets
9. Hidden characters (BOM, whitespace, invisible tabs)
Invisible characters can silently break a CSV:
- BOM (byte-order mark) at the beginning of the file
- leading/trailing spaces in headers
- hidden tabs between fields
How to fix it
- Save files as UTF-8 without BOM
- Trim whitespace automatically
- Validate files before import
10. Editing CSV files directly in Excel
Excel is powerful — but it frequently damages CSV files without warning:
- leading zeros vanish
- dates auto-convert
- long numbers are rounded
- the encoding changes on save
- number formats vary by region
How to fix it
- Use a dedicated CSV editor instead of Excel
- Only view CSVs in Excel, never edit/save
- Define strict formatting rules for your workflow
Conclusion
CSV is a simple, reliable, and universal format — but only when handled correctly. The majority of issues come from inconsistent standards, encoding mismatches, improper quoting, and tools like Excel automatically changing values.
By following consistent rules for delimiters, encoding, quoting, line endings, headers and data formats, you can eliminate nearly all CSV problems. Combined with proper validation or a dedicated CSV tool, your workflows become significantly more stable and efficient.