Subnet Highlighter by Link
Automatically highlights CIDR subnet masks on any page and shows IP count on hover
Available on Firefox for Android™Available on Firefox for Android™
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About this extension
Subnet Highlighter automatically scans every page and highlights all CIDR subnet masks — both IPv4 (/0–/32) and IPv6 (/0–/128). Hover over any highlighted mask to instantly see detailed network information.
IPv4 shows:
- Network & broadcast address, first/last host
- Total IPs, usable hosts, subnet mask, wildcard
- Binary mask representation
- Class (A/B/C), Private/Public (RFC1918)
- Parent network, host offset, reverse DNS zone (PTR)
- Subnets if split into /28, /29, /30
IPv6 shows:
- Network address, first/last host
- Total addresses (as power of 2)
- Type: Global Unicast, Link-local, ULA, Multicast, Loopback
- Parent network, reverse DNS zone (ip6.arpa)
- Subnets if split
IPv4 masks are highlighted in yellow, IPv6 in blue. Works on any page including wikis, monitoring dashboards, NOC tools, and RIPE/BGP looking glasses.
IPv4 shows:
- Network & broadcast address, first/last host
- Total IPs, usable hosts, subnet mask, wildcard
- Binary mask representation
- Class (A/B/C), Private/Public (RFC1918)
- Parent network, host offset, reverse DNS zone (PTR)
- Subnets if split into /28, /29, /30
IPv6 shows:
- Network address, first/last host
- Total addresses (as power of 2)
- Type: Global Unicast, Link-local, ULA, Multicast, Loopback
- Parent network, reverse DNS zone (ip6.arpa)
- Subnets if split
IPv4 masks are highlighted in yellow, IPv6 in blue. Works on any page including wikis, monitoring dashboards, NOC tools, and RIPE/BGP looking glasses.
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Permissions and data
Required permissions:
- Access your data for all websites
Data collection:
- The developer says this extension doesn't require data collection.
More information
- Add-on Links
- Version
- 1.9
- Size
- 19.17 KB
- Last updated
- 7 days ago (Aug 31, 2026)
- Related Categories
- License
- MIT License
- Version History
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