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CSV Studio

Open CSV files that are slow or garbled in Excel and view, search and edit them right away in your browser. Combine, split and save as CSV (UTF-8 with BOM, Shift_JIS), Excel or JSON on one screen.

On-device・No upload

Your files and input are processed only inside your browser on this device and are never uploaded to our servers.

Drop a file here

or

Files are processed in this browser on your device and never uploaded.Accepts: CSV / TSV / TXTUp to 100 MB per filePaste (Ctrl+V) also works

How to use

  1. Drop a CSV, TSV or TXT file or click “Choose files”. You can also paste table text.

  2. Encoding, delimiter and quote character are detected automatically. If columns look wrong, change them in the settings above and toggle “First row is a header”.

  3. Select a cell and press Enter, double-click or just type to edit. Use the search box and the “Filter & sort”, “Columns” and “Edit & replace” tabs to shape the table. Undo with Ctrl+Z.

  4. Use “Combine” to append other CSV files, or “Split” to break the data up by rows, number of files or column value.

  5. In “Save”, choose CSV, TSV, Excel or JSON plus encoding and line endings, then download.

What it does

Smooth with large files

Files are parsed in a Web Worker with progress and cancel. The table only renders visible rows and columns, handling up to 100 MB and 20 million cells per file (e.g. 1,000,000 rows × 20 columns).

Encoding and delimiter detection

Detects Shift_JIS, UTF-8 (with or without BOM), EUC-JP and UTF-16, and comma, tab, semicolon or pipe delimiters. Switch to any single-character delimiter, single quotes or no quoting.

Spreadsheet-style editing with undo

Edit with Enter, F2, Tab and arrow keys, paste ranges from Excel, add and delete rows and columns, rename headers, reorder and hide columns, find and replace (regex supported) and fill blanks from above — with up to 100 undo steps.

Sorting and filtering for real business data

Stable sorting as numbers, natural order (2 < 10) or code point order, and filters for contains, equals, regex, blank and numeric comparisons. Values such as “1,234”, “¥500” and “▲300” compare as numbers; codes with a leading zero stay text.

Combine, split and save in one place

Append other CSV files matched by header name or position, split by rows, file count or column value into a ZIP, and save as CSV, TSV, Excel or JSON. Characters that Shift_JIS cannot represent are listed with their row and column.

Pinpoints broken rows

Rows with a different column count, unclosed quotes and quotes inside values are reported with their record numbers; click a number to jump to that row.

Use cases

  • Quickly inspect and search a CSV with hundreds of thousands of rows that Excel struggles to open
  • Fix a few values in a Shift_JIS export from a business system and save it back in the same format
  • Combine monthly or per-branch CSV files into one, or split a file per region or owner
  • Find the exact rows that break an import (wrong column count, unclosed quotes)
  • Convert CSV to JSON (an array of objects) for code or test data

Supported formats

Input

CSV (.csv)TSV (.tsv / .tab)Text (.txt / .psv)Pasted textUTF-8 / Shift_JIS / EUC-JP / UTF-16 / ISO-2022-JP

Output

CSV / TSV (UTF-8 with BOM / UTF-8 / Shift_JIS / EUC-JP / UTF-16)Excel (.xlsx)JSON (array of objects)ZIP (when splitting)

Capability matrix

FeatureSupportNotes
Automatic and manual encoding and delimiterSupportedDelimiter: any single character
Large files (virtual scrolling, worker parsing)SupportedUp to 100 MB / 20 million cells
Cell editing, add/delete rows and columns, undo/redoSupportedUp to 100 steps
Sort, filter, find and replace (regex)Supported—
Multi-column sortPartialOne column at a time; the sort is stable, so sort by the least important column first
Combine CSV files (append rows)SupportedMatch by header name or position
Key-based joins (VLOOKUP-style) and merging duplicatesNot supportedUse the Excel Merge and Deduplicate tools
Split by rows, file count or column value (ZIP)SupportedUp to 1,000 files
Save as CSV, TSV, Excel or JSONSupportedExcel: up to 1,048,576 rows
Range selection and multi-cell copyPartialCopy one cell at a time; pasting ranges works
Open Excel files (.xlsx) or calculate formulasNot supportedCSV and TSV only

Limits & notes

  • Up to 100 MB and 20 million cells per file (also for files you append). Devices with little memory may fail on smaller files.
  • Sort by one column and filter by AND-combined conditions. Editing cells after filtering does not hide rows automatically; click “Re-apply”.
  • Splitting creates at most 1,000 files and Excel (.xlsx) output holds up to 1,048,576 rows. Values saved to Excel and JSON are text.
  • Each regular-expression run is stopped after 5 seconds. Delimiters must be a single character.
  • Edits are lost when you close the page (nothing is stored in the browser or on a server). Save your file when done.

Privacy & safety

Reading, viewing, editing, combining, splitting and building downloads all happen in your browser. Your data is never sent to or stored on a server.

FAQ

How can I open a CSV file that is too large for Excel?
Drop it here: it is parsed in your browser and only the visible part of the table is drawn, so files up to 100 MB and 20 million cells (for example 1,000,000 rows × 20 columns) work. Files over Excel’s 1,048,576-row limit can be split into Excel-sized parts in the Split tab.
Can I edit and save a Shift_JIS CSV without garbling it?
Yes. The encoding is detected when the file is read, and choosing Shift_JIS in the Save tab writes it back the same way. Characters that Shift_JIS cannot represent (such as emoji) are listed with their row and column.
Can I combine several CSV files into one?
Add files in the Combine tab and their rows are appended below the current table. Match columns by header name or by position, and optionally add a column with the file name.
Can I split a CSV by number of rows or by value?
Yes. In the Split tab, split every N rows, into N equal files, or by a column value (for example by region). Each file includes the header row and everything downloads as one ZIP.
Can I convert CSV to JSON?
Choose JSON in the Save tab to get an array of objects keyed by the header (UTF-8). All values are strings.
Is my data uploaded?
No. Everything runs in your browser and your data never leaves your device.

Related tools

CSV Encoding Fix

Convert CSV files that show garbled text in Excel to UTF-8 with BOM or Shift_JIS, with automatic encoding detection. Mojibake that was already saved, such as “日本語”, can usually be restored too.

CSV, JSON, XML & Excel Converter

Convert between CSV, TSV, JSON, JSON Lines, XML and Excel (.xlsx) by pasting or opening a file. Values stay as text by default, so zero-padded postal codes, phone numbers and long IDs are never changed. Everything runs in your browser; your data is not uploaded.

Data Health Check

Open a CSV or Excel table to get a list of problems — blanks, duplicates, spelling variants, garbled text and more — ranked by severity, a 0–100 health score and a profile of every column. Click a finding to see the affected rows; fixable problems link to the right tool.

Excel Cleanup

Tick what to fix and clean up spaces, character widths, dates and numbers across a whole Excel or CSV file at once. Changed cells are highlighted, and you can save as Excel or CSV.

Excel Compare

Load an old and a new Excel or CSV file to see added, removed and changed rows, with every changed cell shown as “old → new”. Save the result as a colour-coded Excel report or CSV.

Excel Deduplicate

Find duplicate rows in an Excel or CSV file by the columns you choose, ignoring the variations you choose, then remove them or merge each group into one row. Review every group, change which row survives, and save as Excel or CSV.

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