codecrafters.io

.io crawl

First seen 2026-04-11 · Last seen 2026-05-18 · ok HTTP/1.1 200 706 ms crawled 2026-05-18

US · 216.150.1.1 · AS16509 Amazon.com, Inc.

Reputation 94/100 dmarc monitor-only

Classifying

HTML metadata

Title: CodeCrafters | The Hardest Programming Challenges on the Internet
Description: Build your own Redis, Git, SQLite, and more from scratch. Advanced challenges designed for experienced engineers, used by developers at Google, OpenAI, and Vercel.
Language: en
Canonical: https://codecrafters.io

Open Graph

title: CodeCrafters | The Hardest Programming Challenges on the Internet
description: Build your own Redis, Git, SQLite, and more from scratch. Advanced challenges designed for experienced engineers, used by developers at Google, OpenAI, and Vercel.

Technology

CDN: Vercel
CMS: Next.js

Analytics

Google Tag Manager

Third-party hosts loaded (5)

www.googletagmanager.com×2
beacon-v2.helpscout.net×1
lobbyside.com×1
us-assets.i.posthog.com×1
us.i.posthog.com×1

Social

Contact

Email

sarup@codecrafters.io

DNS records live

NS

ns1.digitalocean.com
ns2.digitalocean.com
ns3.digitalocean.com

MX

1 aspmx.l.google.com
10 alt3.aspmx.l.google.com
10 alt4.aspmx.l.google.com
5 alt1.aspmx.l.google.com
5 alt2.aspmx.l.google.com

TXT

Show 10 TXT records

stripe-verification=1089f3cde7a2c01b6dc539a915b9600104c74f456d6ffe5ed63674d51d3e3700
knbc407p0ksxmfhp97cf31qny73mgw1r
1gs62vtv041dwc01vyl47dfnrwh9ywdp
google-site-verification=AGm60ZhZCnOeDzW--6T0Pp940BXJDapHg05sXL4Es5M
_63vxcktqxnd1e5wq1sge35orgm6cm4x
google-site-verification=ZD5_bhJT0PfdQDTic8VGN1ERtYOJ8cuIXm9kQLd5NsI
google-site-verification=VkEBUXig99mOlEuWre0xMpn2Ytf1rL-0_pSdXjUWdFY
mailerlite-domain-verification=ac368294fbc1b085298f3a3f86425422019e7812
_iokocpg8xmbrnfgliu9fhjsi6p35cwp
ahrefs-site-verification_6cf0bd79ac88aab9989d5feb019e947510658a1e66a351928841f7af113fb5c2

Email authentication partial

SPF

v=spf1 a mx include:_mailcust.gandi.net include:helpscoutemail.com include:_spf.google.com include:_spf.mlsend.com ~all

softfail (~all)

DMARC

v=DMARC1; p=none; sp=none; rua=mailto:re+b74a7b17fede@inbound.dmarcdigests.com; aspf=r; pct=100

policy: none (monitoring only) · sp=none

DKIM

google: v=DKIM1; k=rsa; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAjTMFKc8ssoNfVqx1euH+qXylh4MhxDLS3/W3hCHwBD+hNRStJ8wi8MEE4I7MLqVZoiHDChJnXTUMLM…
s1: k=rsa; t=s; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA4/bjFoqUqLBle0tLTvfZy1dF3EDte8QNX2M3/3p4ampHWW5kUFLydUpOx8JB+pt0GTd0EraVKLZaF4vAP+…
s2: k=rsa; t=s; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAuLg26MXnvqPPyaZZiTv1MkX/7DXEcrbL/nNV3R2OaBfs6XSDkQ973ZBb3938J+B5wJUOHbX3GLEDQythu+…

selectors probed

Certificate (current)

R13

from 2026-05-16 to 2026-08-14

Expires in 87 days

Full certificate history on crt.sh ↗

HTTP security headers

Header hygiene 75/100 Checked live page: https://codecrafters.io/

present

strict-transport-security
x-frame-options
x-content-type-options
referrer-policy

findings

missing Content Security Policy
missing Permissions Policy

Header values

referrer-policy: strict-origin-when-cross-origin
x-frame-options: DENY
x-content-type-options: nosniff
strict-transport-security: max-age=63072000