Detect and fix CSV errors
Check encoding issues, duplicate IDs, and invisible characters in your browser. No upload to any server—keep your data safe and improve quality on the spot.
Start CSV checkCommon CSV issues
- Encoding / garbled text — Text breaks when opened in Excel. Imports fail due to UTF-8 vs regional encoding mismatch.
- Duplicate IDs — The same ID in multiple rows causes DB errors or unintended overwrites when merging.
- Invisible characters — Copy-paste or imported data can contain hidden control characters or spaces that break comparison and search.
CSV Checker detects and fixes these inside your browser only. Your data never leaves your device.
Real-world workflows
Designed for quick diagnosis: upload once, pinpoint the cause, fix, and ship. No “mystery import errors”.
Pre-import validation
Catch header mismatch, column count drift, empty rows, BOM, and delimiter issues before your DB or pipeline rejects the file.
Release & batch diffs
Compare “previous vs current” deliveries and see added/deleted/changed rows at a glance to speed up review.
Fix Excel garbled text
Detect encoding mismatches and export as UTF-8 (BOM) to prevent broken text when opening in Excel.
Features
CSV validation
Auto-detect headers, delimiter, column count, empty rows, and BOM so you can spot format issues quickly.
CSV compare
See differences as added, deleted, and changed rows with color highlighting. WinMerge-style view for faster review.
Data cleaning
Remove invisible characters, trim spaces, and detect duplicate IDs. Fix in one click and download.
How it works (4 steps)
- 1 Upload — Select or drag & drop your CSV
- 2 Analyze — Errors and warnings are detected automatically
- 3 Fix — Use the fix-all button to resolve issues
- 4 Download — Save the corrected CSV
Who it's for
Engineers
Validate CSV before DB import, compare production data, or check batch files in advance.
Data analysts
Check data quality for analysis and find duplicates, missing values, or encoding issues.
Office workers
Fix garbled text before opening in Excel and run duplicate checks on lists and rosters.
Choose a tool
Pick the tool that fits your task
Single CSV check
Quick format & error check
Header and data format validation
1. Select file → 2. Auto analysis → 3. View results Select CSV to check →Compare two files
See differences, additions, deletions
WinMerge-style row and column diff
1. Select files → 2. Auto analysis → 3. View results Select two CSVs to compare →Encoding recovery
Convert to UTF-8 BOM for Excel
Auto-detect Shift-JIS, EUC-KR, CP949
1. Select file → 2. Auto-detect → 3. Download Fix garbled file →CSV Converter
Convert to SQL INSERT & JSON
Instant SQL & JSON export from CSV
1. Select CSV → 2. Preview → 3. Copy or Download Convert CSV now →
CSV Splitter
Split large CSV into multiple files
Split by row count · Download as ZIP or individually
1. Select file → 2. Set rows per file → 3. Split & download Split CSV →Developer Tools
Essential developer utilities, right in your browser. All processing happens locally — nothing is sent to a server.
JSON Formatter
Format, validate and minify JSON instantly
Includes real-time validation
1. Paste JSON → 2. Format → 3. Copy Format JSON →Regex Tester
Test regular expressions with real-time highlighting
Common patterns included
1. Enter pattern → 2. Live match → 3. View results Test regex →Timestamp Converter
Convert Unix timestamps across multiple timezones
6 timezones at once
1. Enter timestamp → 2. Auto convert → 3. Copy Convert timestamp →SQL Formatter
Format and beautify SQL with keyword auto-uppercase
Supports MySQL, PostgreSQL and more
1. Paste SQL → 2. Select dialect → 3. Copy Format SQL →Base64 Encoder
Encode and decode Base64 for text and files
Supports text and files
1. Select text/file → 2. Encode → 3. Copy Encode Base64 →URL Encoder
Encode, decode and parse URLs with Query String analysis
Includes URL parser and Query builder
1. Enter URL → 2. Encode/Parse → 3. Copy Encode URL →Hash Generator
Generate MD5, SHA-256 hashes and verify file integrity
MD5, SHA-256, SHA-512 at once
1. Enter text/file → 2. Auto generate → 3. Verify Generate hash →JWT Decoder
Decode JWT tokens and check expiration in real time
Real-time expiration countdown
1. Paste JWT → 2. Auto decode → 3. Check expiry Decode JWT →Cron Parser
Parse cron expressions into human-readable descriptions
Next 10 run times + visual builder
1. Enter cron → 2. Read description → 3. Check times Parse cron →Guides by tool
Open the tool you need, then use these articles when imports fail, text looks wrong, or you want a step-by-step workflow.
Trust & transparency
Clear boundaries help you use data tools with confidence. Here’s what happens (and what doesn’t) when you use CSV Checker.
In-browser processing
Your CSV is processed in your browser. We don’t upload your file to our server.
No file retention
We don’t store your CSV contents on our server. You control downloads and exports.
What we check
Encoding, delimiter, column mismatch, empty lines, duplicate IDs, and invisible characters—so imports fail less.
Supported formats & what we recommend
- Files: Plain-text CSV-style data (comma, tab, or semicolon delimiters—auto-detected where possible).
- Encodings: UTF-8, UTF-8 with BOM, and common regional encodings (e.g. Shift_JIS, EUC-KR/CP949) are detected in your browser.
- For Microsoft Excel: Saving as UTF-8 with BOM avoids garbled columns when reopening; use Encoding recovery if the file is already wrong.
- Limits: Huge files depend on your device’s memory; plan row limits are in Terms.
FAQ
Log in to process more rows
Sign in with Google to unlock higher row limits compared to guest access.
Check your CSV now
Upload a file and run error detection and fixes in one go.
Start CSV check