Website Blocker

A Rust-based Windows desktop application that blocks websites by redirecting their domains to 127.0.0.1 in the system hosts file.

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Features

• Block websites permanently or for a timed duration (e.g. 30m, 2h, 1d)
• Remove sites from the block list at any time — hosts file cleaned immediately
• Toggle all blocking on / off with a single button
• Automatically blocks common domain variants (www., m., app.)
• Persists the block list across restarts (blocked_sites.json)
• Creates a hosts.bak backup before every modification
• Safe concurrent writes via CreateFileW with shared file access
• Precise hostname matching — blocking app.com never touches my-app.com

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Technical Details

Item	Detail
Language	Rust 2021
UI	iced 0.10
Blocking mechanism	Modifies C:\Windows\System32\drivers\etc\hosts
Persistence	blocked_sites.json (next to the executable)
Write strategy	CreateFileW with FILE_SHARE_READ | FILE_SHARE_WRITE

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Module Structure

src/
  main.rs        — entry point: startup sanitisation, launches the GUI
  app.rs         — Iced Sandbox: Message enum, view() layout, update() handler
  blocker.rs     — BlockedSites model + all business logic (add/remove/toggle/expire)
  hosts.rs       — all raw hosts file I/O (backup, clean, append, sanitise, write)
  duration.rs    — parse_duration(): human-readable suffix parsing with clear errors
  permissions.rs — check_permissions(): probes write access instead of parsing whoami

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Dependencies

iced         = "0.10"    # GUI framework
serde        = "1.0"     # serialisation derive macros
serde_json   = "1.0"     # JSON persistence
url          = "2.4"     # URL validation and host extraction
windows-sys  = "0.48"    # CreateFileW, FILE_SHARE_READ/WRITE (Windows only)

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Usage

1. Run webblocker.exe as Administrator (right-click -> Run as administrator).
2. Type a website URL in the left input field (e.g. youtube.com or https://www.reddit.com).
3. Optionally type a duration in the right field:
   • 30s — 30 seconds
   • 5m — 5 minutes
   • 2h — 2 hours
   • 1d — 1 day
   • Leave blank for a permanent block.
4. Click Add Website.
5. Click Enable Blocking to activate. The hosts file is updated immediately.
6. Click Disable Blocking to deactivate — all blocker entries are removed from the hosts file at once.

Tip: If a site is still reachable after blocking, restart your browser and/or run ipconfig /flushdns in an Administrator terminal.

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Removing a site

1. Click the Remove button next to the site in the list.
2. The hosts file is cleaned immediately — no need to disable blocking first and no restart required.

Tip: If the site is still reachable after removal, flush DNS: ipconfig /flushdns

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Installation (from source)

# requires Rust — https://rustup.rs
cargo build --release
# binary is at target/release/webblocker.exe

The binary statically links the MSVC C runtime (configured in .cargo/config.toml) so it runs on any Windows machine without extra redistributables.

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Notes

• Administrator privileges are required to write to the hosts file. The app detects this by probing write access directly — no fragile whoami /priv parsing.
• A backup of the hosts file (hosts.bak) is created before every modification.
• Blocking example.com automatically also blocks www.example.com, m.example.com, and app.example.com.
• Timed blocks are expired automatically — they are not written back to the hosts file once their time has passed.
• For full technical detail on every design and implementation decision, see DESIGN.md.