Free online tools for security engineers, DevOps and sysadmins: subnet calculator, hash generators, JWT decoder, password tools and more.https://toolsec.net/en-ushttps://toolsec.net/guides/what-is-credential-stuffing/https://toolsec.net/guides/what-is-credential-stuffing/One breach, many break-ins: how attackers replay leaked passwords across every site — and why reuse, not weak passwords, is the real vulnerability.Wed, 08 Jul 2026 00:00:00 GMThttps://toolsec.net/guides/what-is-a-password-manager/https://toolsec.net/guides/what-is-a-password-manager/You can't memorise a unique random password for 100 sites — and you shouldn't try. How password managers work, and why they're the single best security upgrade.Wed, 08 Jul 2026 00:00:00 GMThttps://toolsec.net/research/most-common-passwords-2025/https://toolsec.net/research/most-common-passwords-2025/'123456' still tops the list, 'admin' jumped to #2, and even P@ssw0rd-style passwords are cracked instantly. The 2025 most-common-passwords data, and what it teaches.Wed, 08 Jul 2026 00:00:00 GMThttps://toolsec.net/guides/what-is-a-subnet/https://toolsec.net/guides/what-is-a-subnet/Subnets and CIDR notation explained in plain English — what /24 really means, how masks work, and how to divide a network without the headache.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/what-is-a-jwt/https://toolsec.net/guides/what-is-a-jwt/How JSON Web Tokens really work — the header, payload and signature, what signing proves, and the security mistakes that bite teams.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/bcrypt-vs-sha256-passwords/https://toolsec.net/guides/bcrypt-vs-sha256-passwords/SHA-256 is fast — which is exactly why it's the wrong way to store passwords. Here's why bcrypt (or Argon2) wins, and how salting and cost factors work.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/how-to-create-a-strong-password/https://toolsec.net/guides/how-to-create-a-strong-password/Forget swapping letters for symbols. Here's what really makes a password strong — entropy, length, uniqueness — and the simple system that beats memorising rules.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/what-is-base64-encoding/https://toolsec.net/guides/what-is-base64-encoding/Base64 turns binary data into safe text — but it is not encryption. Here's how it works, why it grows your data by a third, and when to reach for it.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/hmac-webhook-signatures/https://toolsec.net/guides/hmac-webhook-signatures/How HMAC proves a message came from who you think it did — the mechanism behind Stripe and GitHub webhook signatures, and how to verify them safely.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/unix-timestamp-explained/https://toolsec.net/guides/unix-timestamp-explained/Epoch time, demystified: what the number really means, the seconds-vs-milliseconds bug that bites everyone, and why timestamps have no timezone.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/301-vs-302-redirects/https://toolsec.net/guides/301-vs-302-redirects/301 or 302? The wrong choice can quietly tank your SEO. Here's what each redirect means, when to use it, and the chain mistakes to avoid.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/ipv4-vs-ipv6/https://toolsec.net/guides/ipv4-vs-ipv6/Why the internet is slowly moving from IPv4 to IPv6 — the address exhaustion problem, what actually changed, and how the two run side by side.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/md5-vs-sha1-vs-sha256/https://toolsec.net/guides/md5-vs-sha1-vs-sha256/MD5 and SHA-1 are broken — but not for the reason most people think. Here's what each hash is for, why collisions matter, and which to actually use.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/cron-syntax-cheat-sheet/https://toolsec.net/guides/cron-syntax-cheat-sheet/Stop guessing what a cron line does. A quick, practical reference to the five fields, the special characters, and the schedules you'll actually write.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/what-is-a-uuid/https://toolsec.net/guides/what-is-a-uuid/What a UUID actually guarantees, why collisions are a non-issue, and why v7 is quietly replacing v4 for database keys.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/url-encoding-explained/https://toolsec.net/guides/url-encoding-explained/Why spaces become %20 and ampersands become %26 — percent-encoding explained, plus the encodeURI vs encodeURIComponent decision that causes so many bugs.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/json-vs-yaml/https://toolsec.net/guides/json-vs-yaml/JSON and YAML describe the same data in very different styles. Here's how they compare, the YAML traps to watch for, and which to reach for when.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/regex-basics/https://toolsec.net/guides/regex-basics/Regular expressions look like line noise until you learn the handful of building blocks. Here's the beginner's path, with examples you can test as you go.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/what-is-http-basic-auth/https://toolsec.net/guides/what-is-http-basic-auth/The simplest way to password-protect a page — and its big caveat. How Basic Auth works, why HTTPS is mandatory, and where it fits.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/what-is-an-api-key/https://toolsec.net/guides/what-is-an-api-key/What an API key actually is, how it differs from a password or token, and the handful of habits that keep one from leaking into a breach headline.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/hexadecimal-explained/https://toolsec.net/guides/hexadecimal-explained/Why 0xFF beats 11111111: how hexadecimal works, its clean mapping to bytes, and where you'll meet it — colors, addresses, hashes and more.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/what-is-gdpr/https://toolsec.net/guides/what-is-gdpr/GDPR in plain English: who it covers, the rights it grants, the two fine tiers (up to 4% of turnover), and where to start. Educational, not legal advice.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/what-is-ransomware/https://toolsec.net/guides/what-is-ransomware/How ransomware actually works, why the ransom is often the smallest cost, and the handful of defenses that make the biggest difference.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/what-is-a-hash-function/https://toolsec.net/guides/what-is-a-hash-function/What a hash function actually does, the properties that make it useful, and the difference between a cryptographic hash and a hash for storing passwords.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/what-is-an-ip-address/https://toolsec.net/guides/what-is-an-ip-address/What an IP address is and how it routes your traffic — public vs private, static vs dynamic, and why your phone and your router don't share the same one.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/what-is-two-factor-authentication/https://toolsec.net/guides/what-is-two-factor-authentication/Why a password alone isn't enough — how 2FA works, the difference between SMS codes, authenticator apps and hardware keys, and which to choose.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/subnetting-cheat-sheet/https://toolsec.net/guides/subnetting-cheat-sheet/A no-fluff subnetting reference: the CIDR-to-mask-to-hosts table, the powers-of-two shortcut, and the boundaries people always get wrong.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/encoding-vs-encryption-vs-hashing/https://toolsec.net/guides/encoding-vs-encryption-vs-hashing/Three words that get mixed up constantly — and confusing them causes real security bugs. Here's the clear distinction, with examples of each.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/what-is-a-data-breach/https://toolsec.net/guides/what-is-a-data-breach/What counts as a data breach, the causes behind most of them, why the true cost dwarfs the headline fine, and how to prepare before one happens.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/jwt-vs-session-cookies/https://toolsec.net/guides/jwt-vs-session-cookies/Stateless tokens or server-side sessions? The real trade-offs between JWTs and session cookies — scalability, revocation, and the security gotchas of each.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/what-is-a-salt/https://toolsec.net/guides/what-is-a-salt/Why two people with the same password should never have the same hash — what a salt is, how it stops rainbow tables, and how it differs from a pepper.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/what-is-csv-format/https://toolsec.net/guides/what-is-csv-format/CSV looks trivial until a comma appears inside a value. Here's how the format really works — delimiters, quoting rules, and the gotchas that corrupt data.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/hmac-vs-digital-signature/https://toolsec.net/guides/hmac-vs-digital-signature/Both prove a message wasn't tampered with — but only one proves who sent it to a third party. The difference between HMAC and digital signatures.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/how-binary-works/https://toolsec.net/guides/how-binary-works/Why computers count in 1s and 0s, how to read a binary number, and how to convert to and from decimal — the foundation under bits, bytes and hex.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/guides/security-roi-explained/https://toolsec.net/guides/security-roi-explained/How to turn 'we should invest in security' into a number leadership respects — the ROSI model, with the inputs and pitfalls explained.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/research/how-many-cves-per-year/https://toolsec.net/research/how-many-cves-per-year/Vulnerability disclosures hit a record 48,185 in 2025 — roughly 133 a day. The year-by-year numbers, why the curve is bending upward, and what it means for defenders.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/research/ipv6-adoption-2026/https://toolsec.net/research/ipv6-adoption-2026/In March 2026, IPv6 quietly hit a milestone: for the first time, the majority of Google's traffic ran over IPv6. Here's what the data shows — and why sources disagree.Sat, 27 Jun 2026 00:00:00 GMThttps://toolsec.net/research/password-crack-time/https://toolsec.net/research/password-crack-time/A computed brute-force time table by password length and character set — showing exactly why length beats complexity. Transparent, reproducible model.Sat, 27 Jun 2026 00:00:00 GMT