Why this tool is useful
Use anonymization before sharing diagnostic samples when full host identifiers are unnecessary; choose stricter prefixes when a dataset could still be identifying in context.
Browser & Privacy · runs locally
Local IP Address Anonymizer
Mask IPv4 and IPv6 host bits with independent prefixes to prepare lower-risk logs, examples and support snippets entirely in the browser.
Ready. Your working data stays in this browser.
How it works
Each strict address becomes an unsigned integer, all bits after the selected prefix are cleared, and the output includes the retained CIDR length so the transformation is auditable.
Practical example
With /24 and /64 settings, 203.0.113.77 becomes 203.0.113.0/24 and 2001:db8:abcd:1234:5678::9 becomes 2001:db8:abcd:1234::/64.
Validation
The calculation is deterministic and explains validation errors instead of silently changing invalid input.
Privacy boundary
Input and output remain in this tab. Copy and download happen through browser APIs without a server upload.
Result passport
Every run reports its tool mode, timestamp and input/output size so transformed data can be audited.