CSV Viewer & Converter

• Fully client-side. CSV files are read via the File API and parsed with JavaScript. No content is transmitted to any server.
• No tracking of content. The tool does not record which files you open or what filters you apply. There is no analytics on data content.
• No automatic saving. Data is held in memory only. Reloading the page clears everything.
• Encoding. Files are decoded as UTF-8. If a file uses a different encoding (like Latin-1 or Shift-JIS), some characters may appear garbled. Most modern CSVs are UTF-8.
• Large files. Files up to a few megabytes work well. Very large files may be slow because parsing and rendering happen in memory. Sorting and filtering on tens of thousands of rows is generally fine on modern devices.
• Read-only viewer. This tool does not edit cells. To change data, edit the source file in a spreadsheet application and re-upload it.

A practical guide to CSV: parsing, quirks and conversion

CSV — comma-separated values — is one of the oldest and most widely used data formats. Every spreadsheet application can export it, every database can import it, and almost every programming language has a library for reading it. Its simplicity is its strength: a CSV file is just text, and you can open one in any editor. But that simplicity also hides a number of quirks that trip up naive parsers, and understanding them makes the difference between a tool that works for spreadsheets and one that works for real-world data.

The rules that matter

RFC 4180 is the closest thing CSV has to an official specification. Its key rules are:

• Records are separated by newlines. Either \n or \r\n works, and a robust parser handles both.
• Fields are separated by a delimiter. Comma is standard, but semicolon and tab are common in regions where the comma is used as a decimal separator.
• Fields containing the delimiter, a newline, or a double quote must be quoted. The whole field is wrapped in double quotes.
• Double quotes inside a quoted field are escaped by doubling. A literal " becomes "". This is the rule that most homegrown parsers miss.

Why the delimiter matters

An exported file from a European spreadsheet application often uses semicolons because commas are the decimal separator in many European locales. Files exported from database tools often use tabs. A good CSV parser either detects the delimiter automatically or lets the user choose. Detection usually works by counting candidate delimiters on the first several lines and picking the one that produces the most consistent number of columns.

Converting CSV to JSON

JSON has become the default format for APIs and config files, so converting CSV to JSON is a common task. The standard approach is to treat the first row as a header, then map each subsequent row to an object where the keys are the header names. This produces readable, self-describing data. When a file has no header, each row becomes an array of values instead, preserving order without imposing names. Both shapes have their uses — objects are more readable, arrays are more compact and easier to process programmatically.

Common pitfalls to watch for

• Quoted commas. A value like "Smith, John" contains a comma that is not a field separator. A naive parser will split it into two fields.
• Quoted newlines. A value like "Line one\nLine two" spans multiple lines but is one field. Simple line-based splitting fails here.
• Escaped quotes. The value He said ""hello"" decodes to He said "hello". Both the encoding and decoding need to be handled.
• Byte order marks. Some files start with an invisible BOM character. If it is not stripped, the first header name may look corrupted in the output.
• Inconsistent columns. Some rows may have fewer columns than the header. A good converter either pads or reports this clearly.

About this tool

This CSV viewer and converter is part of the TempScript free online tools collection. It runs entirely in your browser, requires no account, and never sends your data anywhere. If you work with data and text regularly, you may also find our JSON formatter and URL encoder and decoder useful.