For Free2S, here are some useful online tools you could consider providing:
IP Tools:
IP Address Lookup
Ping/Traceroute
DNS Lookup
WHOIS Lookup
Reverse IP Lookup
Unit Converters:
Length, Weight, Temperature, Volume Converters
Currency Converter (with live exchange rates)
Time Zone Converter
Text Tools:
Text Case Converter (upper, lower, title case)
Word/Character Counter
Text Reverser
Text Diff Checker
Password Generators:
Strong Password Generator (with customizable options like length, special characters, etc.)
Passphrase Generator
File Tools:
PDF to Word/Excel converter
Image Format Converter (e.g., JPG to PNG)
Zip and Unzip Tools
File Size Reducer (for images, PDFs)
Web Tools:
Website Speed Test
Mobile Compatibility Test
Meta Tag Analyzer
Page Redirect Checker
Math Tools:
Simple and Scientific Calculators
Percentage Calculator
Loan Calculator
BMI Calculator
Code Tools:
JSON Formatter and Validator
HTML/CSS Minifier
QR Code Generator
Markdown to HTML Converter
SEO Tools:
Keyword Density Checker
Backlink Checker
Meta Tag Extractor
Date & Time Tools:
Age Calculator
Countdown Timer
Epoch Converter (Unix timestamp)
Calendar Generator
These tools would attract a broad range of users, offering practical utility while driving traffic to your site. You can continue to expand as you gather feedback on what users find most valuable.