443
443 is the standard port for HTTPS — encrypted web traffic.
- Odd
- Prime
Where 443 fits
Why 443 is special
443 is the number that made the padlock possible. Plain HTTP took port 80 and encrypted HTTP was assigned 443 alongside it, so a browser can tell from the address alone which it is speaking. As the web moved to encryption by default, 443 went from the exception to carrying nearly all of it.
Same number, different meanings
How 443 is understood across different contexts — never implying one meaning because of another.
- Mathematics
443 is the number that made the padlock possible. Plain HTTP took port 80 and encrypted HTTP was assigned 443 alongside it, so a browser can tell from the address alone which it is speaking. As the web moved to encryption by default, 443 went from the exception to carrying nearly all of it.
- Everyday life
The padlock indicates that the connection to the site is encrypted and that the certificate matches the domain. It makes no claim about who runs the site or whether it is trustworthy, which is why phishing sites routinely display one.
- History
HTTPS was introduced by Netscape in 1994 and remained a minority of web traffic for two decades, largely because certificates cost money and required manual renewal. Automated free issuance from 2016 moved encrypted traffic past half of page loads within about two years.
- Science
IC 443, the Jellyfish Nebula, is a supernova remnant whose expansion into an adjacent molecular cloud produces distinctive shocked emission.
- Technology & computing
Assigning encrypted HTTP its own port meant a browser could tell from the URL alone which protocol to speak, before any connection was made. As the web moved to encryption by default, traffic shifted almost entirely from 80 to 443 — one of the largest changes in what the internet carries, visible only as a number.
Factors & digit properties
- Divisors (2)
- 1, 443
- Prime factorisation
- 443
- Digit sum
- 11
- Digital root
- 2
Representations
- Decimal
- 443
- Binary
- 110111011
- Octal
- 673
- Hexadecimal
- 1bb
- Roman numeral
- CDXLIII
- Scientific notation
- 4.430 × 10^2
Other mathematical patterns
- Deficient number
- Sophie Germain prime
Related numbers & connections
Port 443 is an IANA assignment. The number itself carries no meaning; its authority comes entirely from the registry entry.
OpenVPN's own port is easy to identify and therefore easy to block, so it is frequently moved to 443 where it cannot readily be told apart from ordinary web traffic.
View 1194 →Numbers Around Us
- appears inNumbers assigned as identifiers
why?
Strength 0.50, confidence "high".
- appears inNumbers that make the internet work
why?
Strength 0.50, confidence "high".
Other connections
- contrasts with1194
why?
Strength 0.50, confidence "high".
- contrasts with9418
why?
Strength 0.50, confidence "high".
- contrasts with80
why?
Strength 0.50, confidence "high".
- is associated with993
why?
Strength 0.50, confidence "high".
- is associated with3546
why?
Strength 0.50, confidence "high".
- is associated with2818
why?
Strength 0.50, confidence "high".
- is associated with127
why?
Strength 0.50, confidence "high".
Everyday life
The padlock indicates that the connection to the site is encrypted and that the certificate matches the domain. It makes no claim about who runs the site or whether it is trustworthy, which is why phishing sites routinely display one.
DocumentedEveryday lifeGeography: GlobalPeriod: 1994–
History
HTTPS was introduced by Netscape in 1994 and remained a minority of web traffic for two decades, largely because certificates cost money and required manual renewal. Automated free issuance from 2016 moved encrypted traffic past half of page loads within about two years.
DocumentedHistoryGeography: International — IANA and IETFPeriod: 1994–
Science
IC 443, the Jellyfish Nebula, is a supernova remnant whose expansion into an adjacent molecular cloud produces distinctive shocked emission.
DocumentedSciencePeriod: 1890s–
Technology & computing
Assigning encrypted HTTP its own port meant a browser could tell from the URL alone which protocol to speak, before any connection was made. As the web moved to encryption by default, traffic shifted almost entirely from 80 to 443 — one of the largest changes in what the internet carries, visible only as a number.
DocumentedTechnology & computing
Common questions
Is 443 a prime number?
Yes, 443 is prime — it has exactly two positive divisors: 1 and itself.
What are the factors of 443?
The factors of 443 are 1, 443.
What is 443 in Roman numerals?
443 in Roman numerals is CDXLIII.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 4 reviewer-confirmed records, sourced and reviewed before publication.
Last reviewed: 3 August 2026