Hosts File Generator and Parser

Features

• Parse mode lists every IP → hostname entry
• Multiple hostnames on one line are listed separately, not merged
• Whole-line and trailing # comments handled apart
• Checks for invalid IPs, duplicate IPs and duplicate hostnames
• Marks IPv6 entries and 0.0.0.0 blocking entries
• Generate mode turns one hostname per line into a hosts file
• Spaces and tabs between fields are both accepted
• Runs entirely locally, with no network requests

How to use

1. Choose Parse or Generate
2. Parse: paste a whole hosts file
3. Generate: one hostname per line, optionally as "IP hostname", with the default IP filling in the rest
4. Copy the generated file or the check results

FAQ

What is the difference between 0.0.0.0 and 127.0.0.1 for blocking?

Both stop a domain resolving to its real address, but `0.0.0.0` is the safer, more common choice: it points at an invalid address, so connections fail immediately. `127.0.0.1` points the domain at your own machine, and if something happens to be listening on that port you may connect to an unexpected service. That is why modern block lists use `0.0.0.0`.

How many hostnames can one line hold?

As many as you like. Hostnames on one line are aliases that resolve to the same IP — `127.0.0.1 a.local b.local` makes both names point at your machine. This tool lists them individually when parsing (rather than merging them) and accepts `IP name1 name2` when generating.

Why flag duplicate hostnames?

Because when the same hostname maps to different IPs on different lines, only the first entry takes effect and the rest are ignored — a confusing "I changed it and nothing happened". Listing the duplicates lets you confirm whether a stale entry is still sitting there.

Where is the hosts file, and do I need to reboot?

It is `/etc/hosts` on Linux and macOS, and `C:\Windows\System32\drivers\etc\hosts` on Windows — both need administrator rights. Changes usually take effect immediately, with no reboot; but a browser may have cached the DNS answer, so restart it or flush the OS cache (on Windows, `ipconfig /flushdns`).