File conversion for developers
Format conversions developers run into in real workflows — config files, data interchange, fonts, and assets.
Developers run into format conversion in surprising places: YAML config files that need to become JSON for an API, CSV exports that need to become a database import, fonts that need to be web-deployed, screenshots that need to become favicons. Most of these aren't really 'developer' tasks — they're side quests that block the actual work. The right tooling makes them disappear.
This page collects the conversions and guides that come up most for developers: config and data formats, web deployment assets, and the gotchas that bite when you're moving data between systems.
Recommended converters for developers
The conversions that come up most in developers' workflows, with a quick note on when to use each.
YAML → JSON
Convert human-edited config files to JSON for API consumption.
JSON → YAML
Make machine-generated JSON readable for human config editing.
CSV → JSON
Transform tabular data exports into structured records for web apps.
CSV → XLSX
Hand off CSV data to non-technical stakeholders who prefer Excel.
XML → JSON
Modernize XML-based pipelines into JSON for newer tools.
PNG → ICO
Generate proper Windows favicons from app logos.
TTF → WOFF2
Compress fonts for web deployment with universal browser support.
HTML → PDF
Render HTML reports/invoices as fixed-layout PDFs for distribution.
Developers workflow recommendations
The format and conversion choices that consistently produce the best results for developers.
Use YAML for human-edited config, JSON for machine-to-machine
Kubernetes, GitHub Actions, Docker Compose — these all use YAML because humans edit them. APIs use JSON because parsers are faster and more strict. Convert at the boundary, not in the middle.
Quote string values that look like other types in YAML
Unquoted 'NO', 'yes', '01234' get coerced to boolean/number in YAML 1.1 (the famous 'Norway problem'). Quote any string that could be misinterpreted, or use a YAML 1.2 parser.
UTF-8 with BOM for CSV-to-Excel
Excel detects UTF-8 only when there's a BOM at the start. Without it, accented characters and non-Latin scripts display as garbled. Add the BOM at write time, not in a downstream cleanup.
Subset web fonts to characters you actually use
A font shipped to the browser with full Unicode coverage is 5-10× larger than one subset to your site's actual character set. Subsetting before converting to WOFF2 produces dramatically smaller files.
Recommended reading
In-depth guides relevant to developers' format decisions.
YAML vs JSON: which to use when, and what changes during conversion
YAML and JSON solve the same problem in nearly opposite ways. A practical guide to when to pick each, what conversion preserves and what it doesn't, and the gotchas to know about.
Converting CSV to Excel without breaking dates, numbers, or leading zeros
CSV-to-Excel looks like the simplest conversion possible. Until Excel decides your phone numbers are scientific notation and your ZIP codes have lost their leading zeros. A guide to the gotchas and how to avoid them.
Seven common file conversion mistakes (and how to avoid each one)
Lossy double-encoding. Ignoring transparency. Forgetting OCR. Trusting auto-detected types. The most common file conversion mistakes and the simple practices that prevent them.
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