Guides
Guides
Longer walkthroughs for the problems that bring people here: the file that will not open, the CSV that came out as one column, the dedupe nobody can audit.
- 4 min read
How to Anonymize a Data File Before You Share It
Find the personal data in a file and mask, hash, tokenize or generalize it — on your own machine, with every finding shown for you to confirm before anything is rewritten.
Read more - 5 min read
How to Clean a Data File Without Writing a Script
Fix the twenty things wrong with every export — whitespace, mixed date formats, numbers stored as text, lost leading zeros, bad encoding — in one previewable pass on your own PC.
Read more - 4 min read
How to Compare Two Excel Files and See Exactly What Changed
Compare two Excel, CSV or Parquet files on your own PC: schema drift, added and removed rows, and cell-level differences — with tolerances so float noise is not reported as a change.
Read more - 3 min read
Why Your CSV Opens as One Column — and How to Fix It
A CSV that lands in a single column is almost always a delimiter mismatch: the file uses semicolons and your machine expects commas. Here is why, and three ways to fix it.
Read more - 4 min read
How to Open a CSV File That Excel Will Not Open
Open and read CSV files of any size on Windows. Filter and sort against the file itself rather than a loaded copy, see the detected delimiter and encoding, and never upload anything.
Read more - 4 min read
How to Generate a Data Dictionary From a File You Already Have
Produce a data dictionary from a CSV, Excel or Parquet file: every column with its type, semantic role, null rate, range and sample values. Exports to .xlsx and Table Schema JSON.
Read more - 4 min read
How to Profile a Data File Before You Build Anything On It
Profile every column in a CSV, Excel or Parquet file: inferred type, semantic role, nulls, distinct counts, ranges, outliers and candidate keys — on your own machine, at any file size.
Read more - 4 min read
How to Score the Quality of a Data File — and Show Your Working
Measure a file's data quality across completeness, validity, uniqueness, consistency and structure — with the weights shown, so the score is auditable rather than a black box.
Read more - 3 min read
Excel Not Responding on a Big File — What to Do Instead
Excel hangs, greys out, or reports it is out of resources on a large workbook. Why it happens, what will not help, and how to open the file another way.
Read more - 3 min read
How to Find Duplicates in a File Too Big for Excel
The file that most needs deduplicating is usually the one Excel already refused to open. Find exact, normalized and fuzzy duplicates at any size, with a report of what was found.
Read more - 3 min read
How to Fix Garbled Characters in a CSV (é and Friends)
Café became Café and every accent turned to nonsense. That is an encoding mismatch, not corruption — here is how to read the file correctly and write one Excel opens properly.
Read more - 3 min read
The Best Free CSV Viewer for Windows — What to Look For
What actually separates a usable CSV viewer from a text editor with columns: paging against the file, a visible delimiter guess, and column profiling. Plus the honest alternatives.
Read more - 3 min read
Leading Zeros Disappeared From Your CSV — Why, and How to Stop It
Postcode 02134 became 2134 and your 18-digit IDs turned into scientific notation. That is Excel typing the column on open. Here is how to convert without it happening.
Read more - 3 min read
Online CSV Tools vs Doing It on Your Own Machine
Every free web converter asks you to upload the file first. What that actually means for a spreadsheet of customers or salaries, and when it does and does not matter.
Read more - 3 min read
How to Merge Many CSV Files Into One
Combine a folder of CSV, Excel or Parquet files into a single table on your own PC — even when the columns do not match — with a source-file column so you can tell where each row came from.
Read more - 3 min read
How to Open a Large CSV File When Excel Won't
Excel stops at 1,048,576 rows and gives up long before that. Open a multi-gigabyte CSV on your own PC, read it, filter it, and export just the part you need.
Read more - 3 min read
How to Open a .parquet File on Windows
Windows has no handler for .parquet and every guide says install Python. Open one directly — single file or partitioned folder — and export it to Excel or CSV.
Read more - 3 min read
How to Remove Duplicates and Prove What You Removed
Find and remove duplicate rows in Excel, CSV and Parquet files using exact, normalized or fuzzy matching — and get a report naming every row that went and what it matched.
Read more - 3 min read
How to Split a Large CSV Into Smaller Files
Split by row count, by file size, or by a column's values — with the header repeated in every part, which is the thing hand-rolled splitters get wrong.
Read more - 3 min read
How to Run SQL Against a CSV File Without a Database
Query CSV, Parquet, Excel and JSON files directly with SQL — join across formats, no import step, no server to set up, and nothing uploaded. Free for Windows.
Read more - 3 min read
Text to Columns, on a File Excel Cannot Open
Split one column into several by a delimiter, a fixed width, or a pattern — previewable, repeatable, and on files far past Excel's row limit.
Read more - 3 min read
DataTray vs Excel for Large Files — an Honest Comparison
Excel is the right tool for most spreadsheet work and the wrong one for a multi-gigabyte export. Where each wins, where the row limit bites, and how they work together.
Read more - 3 min read
What Is a Parquet File — and How Do You Open One on Windows?
Somebody sent you a .parquet file and Windows has no idea what it is. What the format is, why data teams use it, and how to open one without installing Python.
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Looking for a one-off conversion instead? The free converters cover the common pairs.