About Xilfy

What we build

Small, focused tools that do one job well: formatting and validating JSON, decoding JWTs, testing regular expressions, compressing images, merging PDFs, checking DNS and SSL, and calculating BMI, calories, loans, and percentages. Every tool page explains what the tool does, how to use it, and answers common questions.

Your data stays with you

Most tools run entirely in your browser. When you format JSON, compress an image, edit a PDF, or generate a password, the data never leaves your device. Tools that need a server, such as DNS, WHOIS, and SSL lookups or the URL shortener, only send what is needed to get the answer. Read the privacy policy for details.

Accuracy and sources

Calculators use published, widely accepted formulas and say which one they use on the page:

• BMI categories follow the World Health Organization adult classification.
• The calorie calculator uses the Mifflin-St Jeor equation, or Katch-McArdle when body fat is known.
• Holiday calendars are built from official public holiday rules for each country.
• Encoders, hashes, and token tools follow the relevant standards, such as RFC 4648 for Base64 and RFC 7519 for JWT.

Health and finance results are estimates for general information, not medical or financial advice.

Contact

Found a bug, a wrong result, or have an idea for a new tool? Get in touch; we read every message.