Settings

Open Settings with the Link Guard button in the message header toolbar, the Link Guard – open settings button in the main toolbar, or from Add-ons and Themes → Link Guard → Options.

Changes take effect only after you click Save changes at the bottom of the page. Open messages update immediately after saving.

General

Enable Link Guard

Turns the protection on or off. When it is off, all links are directly clickable again, no notice or labels are shown, and the toolbar tooltip reads Link Guard is disabled. Your approvals, blocks and lists are kept. On by default.

Show link destinations

Shows the real domain next to links whose text does not name it, for example ↗ shop.example.org after a button labelled Order now. Turn it off if these labels disturb the layout of your messages. On by default.

This setting only hides the neutral destination labels. Warning labels, including the destination they name, are always shown, and the notice always lists every destination.

Your rules

Four cards hold your own permanent decisions. Each takes one rule per line, up to 500 per card. Decisions you make in a message appear here, and you can also edit the lists directly.

Settings page with separate cards for approved hosts, blocked hosts, approved whole domains and blocked whole domains

Card	Format	Effect
My permanent approvals	exact hosts, e.g. `login.example.org`	allows exactly these hosts
Blocked hosts	exact hosts	blocks exactly these hosts; overrides approvals and imports
Approve whole domains	`*.example.org`	allows the domain and all subdomains, except shared-content hosts
Block whole domains	`*.example.org`	blocks the domain and all subdomains; overrides approvals and imports

Rules for writing hosts:

Exact hosts have no wildcard. login.example.org and example.org are different hosts.
Whole-domain rules use *.example.org and include example.org itself. The domain must be a registrable domain according to the bundled Public Suffix List, so *.co.uk or *.github.io are refused with a message naming the entry.
No URLs, paths, ports, user names or IP addresses. Upper case and a trailing dot are normalised; internationalized names are stored in their xn-- form.
An invalid line is reported with its line number, and nothing is saved until it is fixed.

See Approvals and blocks for how these rules combine.

Custom and remote lists

Import allowlists and blocklists from a JSON file or an HTTPS URL. The format and the requirements for remote sources are described in Host lists.

Imported lists: an enabled allowlist, an enabled remote blocklist that updates itself and a disabled one

Importing a list

Choose a JSON file, or enter the HTTPS URL of a list and click Check remote list.
Link Guard validates the list and shows a Preview with its name, type, category and every entry.
Click Stage as disabled list to add it, or Cancel.
Tick Enable list when you have reviewed it, then click Save changes.

Lists always start disabled. A disabled list has no effect.

Managing a list

Each imported list is a card showing its name, type (Allowlist or Blocklist), category and number of entries.

Enable list – turns the list on or off.
View and edit list – shows the entries; you can edit them directly. Blocklists may contain *.example.org entries, allowlists only exact hosts.
Review remote update – for lists loaded from a URL: fetches the current version and shows it as a preview. Stage update replaces the entries and leaves the list disabled until you enable it again.
Update automatically about once a day (replaces local edits) – for remote blocklists only; on by default. See Automatic updates.
Remove list – removes the list on the next save.

Up to 20 lists, each with up to 5,000 entries.

Warnings

Warning settings with built-in toggles and an own regex rule

Built-in warnings

One switch per built-in warning, all on by default:

Domain resembles an approved domain
Internationalized domain name
Link text shows a different host
User name or password in the link
IP address instead of a host name
Public URL shortener
Script or HTML code in the link
Link redirects to a site you have not approved

Switching a warning off removes both the warning and the exact approval it requires. Domain check unavailable cannot be switched off. See Warnings.

My warning rules

Click Add rule to add a row with:

Label – the text shown as the warning, 1 to 60 characters.
Checks – what the pattern is matched against: Host, Full URL or Link text.
Pattern – a case-insensitive regular expression of up to 200 characters.

Remove deletes a row. Up to 50 rules of your own. Errors are reported with the rule number when you save, for example Rule 2: the pattern is longer than 200 characters. The supported syntax is described in Warning rules.

Warning lists

Import rules from a JSON file or an HTTPS URL. As with host lists, a Warning list preview shows every rule; Stage as disabled list adds it disabled, and Enable list turns it on. Show rules lists the rules of an imported list. Remote warning lists change only when you click Review remote update – they never update themselves.

Up to 10 warning lists of up to 50 rules each, and at most 200 rules in effect in total.

Saving

Save changes validates everything on the page and stores it in one step. If something is invalid, a message near the button names the card and line or rule, and nothing is stored.

If your lists changed elsewhere while the page was open – for example because you approved a host in a message – the page says Lists changed elsewhere. Reload this page before saving. Reload the page and repeat your edits; this prevents one change from overwriting the other.