Are these network and DevOps tools free?

Yes — every tool on this site is completely free to use, with no account, signup, paywall or usage limits. Open a tool and start typing.

Is my data uploaded to a server?

No. The tools run entirely in your browser, so tokens, passwords and text never leave your machine. The one deliberate exception is the DNS lookup, which sends your query straight to Cloudflare's public DNS-over-HTTPS resolver (1.1.1.1) — and nowhere else.

What tools are included?

A DNS lookup, an IPv4 subnet/CIDR calculator, a cron expression builder, Base64 and URL encoders, a JSON formatter, a JWT decoder, password/UUID/ULID generators, MD5 and SHA hash generators, a Unix timestamp converter, a regex tester, data-size and number-base converters, an OpenAPI spec explorer and a text encryptor — plus a DevOps cheat sheet.

Do the tools work on mobile?

Yes. Everything runs in any modern browser on desktop or mobile. Because the work happens client-side, the tools stay fast even on a slow connection.

DevOps & Networking Cheat Sheet

The lookups you make every week — cron fields, CIDR masks, common ports, HTTP status codes and DNS record types — on one page.

Bookmark this page for the quick answer; every section links to the interactive tool when you need to compute a real value.

Cron syntax

minute hour day-of-month month day-of-week — five fields, read left to right.

*/5 * * * * — every 5 minutes
0 * * * * — hourly, on the hour
0 3 * * * — daily at 03:00
0 3 * * 1 — Mondays at 03:00
0 0 1 * * — first of the month at midnight
*/15 9-17 * * 1-5 — every 15 minutes, 09:00–17:59, weekdays

Build and sanity-check your own schedule in the Cron Expression Builder.

Subnet masks (IPv4 CIDR)

/8 — 255.0.0.0 — 16,777,214 usable hosts
/16 — 255.255.0.0 — 65,534 hosts
/24 — 255.255.255.0 — 254 hosts
/25 — 255.255.255.128 — 126 hosts
/26 — 255.255.255.192 — 62 hosts
/27 — 255.255.255.224 — 30 hosts
/28 — 255.255.255.240 — 14 hosts
/30 — 255.255.255.252 — 2 hosts (point-to-point)
/31 — 255.255.255.254 — 2 hosts (RFC 3021 point-to-point)
/32 — 255.255.255.255 — a single host

Usable hosts = 2^(32 − prefix) − 2 for the network and broadcast addresses. Work any block interactively in the Subnet / CIDR Calculator.

Common TCP/UDP ports

20/21 FTP — 22 SSH & SFTP — 23 Telnet — 25 SMTP
53 DNS — 67/68 DHCP — 80 HTTP — 110 POP3
123 NTP — 143 IMAP — 443 HTTPS — 465/587 SMTP over TLS / submission
993 IMAPS — 995 POP3S — 1433 SQL Server — 3306 MySQL
3389 RDP — 5432 PostgreSQL — 6379 Redis — 8080 HTTP alternate
9090 Prometheus — 9200 Elasticsearch — 27017 MongoDB

HTTP status codes

200 OK — 201 Created — 204 No Content
301 Moved Permanently — 302 Found — 304 Not Modified — 307/308 Temporary/Permanent Redirect
400 Bad Request — 401 Unauthorized — 403 Forbidden — 404 Not Found
405 Method Not Allowed — 409 Conflict — 422 Unprocessable Content — 429 Too Many Requests
500 Internal Server Error — 502 Bad Gateway — 503 Service Unavailable — 504 Gateway Timeout

Mnemonic: 401 means not authenticated; 403 means authenticated but not allowed.

DNS record types

A / AAAA — hostname to IPv4 / IPv6 address
CNAME — alias pointing at another hostname
MX — mail exchanger that accepts the domain's email
TXT — free-form text: SPF, DKIM, domain verification
NS — the zone's authoritative nameservers
SOA — zone serial number and refresh timers
SRV — service locator carrying a host and port
CAA — which certificate authorities may issue for the domain

Query any of them live in the DNS Lookup.

How do I read a cron expression?

Left to right the five fields are minute, hour, day of month, month and day of week. `*` matches every value, `*/N` means "every N", `A-B` is a range and `A,B` a list. When both day-of-month and day-of-week are set, most crons fire when either matches.

How many usable hosts does a subnet have?

Two to the power of (32 minus the prefix length), minus 2 for the network and broadcast addresses — so a /24 has 254 usable hosts and a /26 has 62. The exceptions are /31 (2 hosts, RFC 3021 point-to-point) and /32 (a single host route).

What is the difference between a 502 and a 504?

Both come from a proxy or load balancer in front of your app. A 502 Bad Gateway means the upstream answered with something invalid (often a crash or connection reset); a 504 Gateway Timeout means the upstream never answered in time.

Related tools

Cron Expression Builder — turn a schedule into an expression
Subnet / CIDR Calculator — full math for any block
DNS Lookup — check what a record actually says
Number Base Converter — masks and octets in binary/hex

🔐 Private by design: every tool runs in your browser. DNS lookups go straight to Cloudflare's DoH resolver (1.1.1.1); nothing else is sent to any server, and nothing is logged.