IP Address Converter
Every representation of an address at once — dotted, binary, integer and hex.
Enter an address on the left.
How it works
An IPv4 address is one 32-bit number. The dotted form everyone writes is a convenience laid over it, not the address itself — which is why the same host can be written several ways that look nothing alike, and why a link can be built to survive a glance.
Why http://2130706433/ reaches localhost
Because 2,130,706,433 is 127.0.0.1 — the same number, written without the dots. Most resolvers accept
that integer, its hexadecimal form 0x7f000001, and dotted octal 0177.00.00.01. All four
reach the same host. A reader skimming a URL sees a long number and moves on; the resolver does not.
These forms are output, not input
Paste 2130706433 here and it is rejected. That is deliberate and worth stating plainly: this page
reports what an address is, so accepting an obfuscated form as input would mean agreeing with the
disguise — you would paste something ambiguous and get back a confident answer about which reading was meant.
Input is strict dotted-quad. The alternative encodings are produced so you can recognise one, not so you can feed
one in.
A leading zero is an error, not a guess
010.1.1.1 is refused. A leading zero means octal to some resolvers and decimal to others, so
010 is 8 or 10 depending on what parses it. Both readings are plausible and they disagree. That
ambiguity is itself the reason the form appears in links that would rather not be read closely.
Example
127.0.0.1 gives binary 01111111 00000000 00000000 00000001, integer
2130706433 and hex 0x7f000001. The binary column is the one to read against a mask —
lining a prefix up against those bits is what makes CIDR arithmetic obvious
rather than arithmetic.
Frequently asked questions
Why does http://2130706433/ reach 127.0.0.1?
Because an IPv4 address is a single 32-bit number, and the dotted form is a convenience rather than the address itself. Most resolvers accept that number written as decimal, as hex (0x7f000001), or as dotted octal — so the same host can be written several ways that look nothing alike. That is why these forms appear in links built to survive a glance.
Why does it reject 2130706433 as input when it shows that form as output?
Deliberately. This tool reports what an address is, so accepting an obfuscated form as input would mean agreeing with the disguise — you would paste something ambiguous and get a confident answer about which reading was intended. Input is strict dotted-quad; the alternative encodings are produced as output so you can recognise one when you meet it.
Why is 010.1.1.1 an error?
Because a leading zero means octal to some resolvers and decimal to others, so 010 is 8 or 10 depending on what parses it. Both readings are plausible and they disagree, so neither is guessed. That ambiguity is itself the reason the form shows up in links that are trying not to be read carefully.
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