Withdata DataFileConverter converts fixed-width text files to JSON locally — single file, batch, or merge multiple Fixed-Width Text files into one JSON. You define the column widths — or let the tool measure them. 100% local, secure, and cross-platform.

Fixed-width text is a plain text format in which every column has a fixed character width and no delimiter is used.

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Why Choose Withdata Fixed-Width Text to JSON Converter?

🔒 100% Local & Secure

Fixed-Width Text files are read and converted on your own computer. Nothing is uploaded to any cloud server.

⚡ Fast Streaming Conversion

Large Fixed-Width Text files are processed in streaming mode with low memory usage — millions of rows within a minute.

📁 Batch & Merge

Batch convert many Fixed-Width Text files to JSON files, or merge multiple Fixed-Width Text files into one JSON.

🔄 Column Widths, No Delimiter

Define the width of every column (N columns need N-1 widths). No delimiter and no quoting are needed.

🖥 Windows, macOS, Linux

Native builds for Windows, macOS and Linux, with a step-by-step GUI wizard and a command line interface.

⏱ CLI & Scheduled Tasks

Save a conversion session and run it automatically from Windows Task Scheduler or crontab.

Full Feature Comparison

Feature	Supported details
Input source	Local fixed-width text, batch files, merged files
Output format	JSON object array, plain JSON array, or JSON Lines (one object per line)
Conversion mode	Single file · merge many Fixed-Width Text files into one JSON · batch (one to one)
Running mode	GUI wizard · command line · scheduled tasks
Source options	Column widths (N-1 widths for N columns), header row, start row, encoding
Output options	Column mapping, encoding, date format, empty value handling
Platform	Windows, macOS, Linux (native, 64-bit)

All Fixed-Width Text to JSON Conversions You Need

Single Fixed-Width Text file → JSON file, step by step in the GUI wizard
Batch convert multiple Fixed-Width Text files → multiple JSON files
Convert Fixed-Width Text to JSON in the command line, and run it as a scheduled task
All Fixed-Width Text conversion tools and all JSON conversion tools

Fixed-Width Text to JSON Notes

Columns are defined by widths, not by a delimiter: for N columns you enter N-1 widths, e.g. 10,25,8.
No delimiter and no quoting are used — spaces are part of the column.
A header row is optional and leading rows can be skipped.
When writing fixed-width output, widths can be detected from the data automatically (measured width + 15% slack, at least 2 and at most 15 extra characters).
The encoding (UTF-8, ANSI, UTF-16, ...) can be detected or set explicitly.

How to Convert Fixed-Width Text to JSON (4 Steps)

Open Withdata DataFileConverter and select Fixed-Width Text as the input type and JSON as the output type.
Load your Fixed-Width Text data — a single file, a folder / list of files for batch conversion, or several files to merge into one.
Check the preview table, then adjust the source options and the output options.
Click Convert — the JSON output is written in seconds. Save the session if you want to run it again from the command line.

Convert Fixed-Width Text to JSON in GUI

In GUI mode the conversion is a step-by-step wizard: choose the Fixed-Width Text source, choose the JSON destination, check the preview, and click Convert. See Withdata DataFileConverter.