---
title: 9 new free tools: cron tester, email header analyzer, IPv6 calculator and more
description: The small checks you reach for a dozen times a week — is this cron expression right, what does this email header actually say — should be a click away. Nine…
canonical: https://watchfor.io/changelog/2026-08-19-free-calculators-and-status-docs
---

[All updates](/changelog/page/7#2026-08-19-free-calculators-and-status-docs) ✨ New Aug 19, 2026 · v 5.7.1

# 9 new free tools: cron tester, email header analyzer, IPv6 calculator and more

The small checks you reach for a dozen times a week — is this cron expression right, what does this email header actually say — should be a click away. Nine new free tools: a cron expression tester with plain-English explanations and next-run previews, an email header analyzer that traces delivery hops and authentication entirely in your browser, IPv6 subnet and error-budget calculators, a JSON formatter with JSONPath testing, an SPF & DMARC record generator, plus timestamp, bandwidth and chmod converters. We also published a full HTTP status code reference in the docs.

Type an expression, read it in plain English, see the next runs.

## The nine tools

Tool What it answers

[Cron expression tester](/cron-expression-tester) What does */15 9-17 * * 1-5 mean, in plain English, and when are the next runs?

[Email header analyzer](/email-header-analyzer) Which servers did this email pass through, how long did each hop take, and did SPF, DKIM and DMARC pass?

[IPv6 subnet calculator](/ipv6-subnet-calculator) How many addresses and /64s are in this prefix, and where does it start and end?

[Error budget calculator](/error-budget-calculator) How much downtime does a 99.9 % SLO allow this month, and how much is left?

[JSON formatter](/json-formatter) Pretty-print or minify JSON, and test a JSONPath against it.

[SPF & DMARC generator](/spf-dmarc-generator) Build a valid record for your domain without memorising the syntax.

[Epoch converter](/epoch-converter) Turn a Unix timestamp into a date and back.

[Bandwidth calculator](/bandwidth-calculator) How long does 40 GB take over a 100 Mbit/s link?

[Chmod calculator](/chmod-calculator) What is 754 , and which number gives the owner write access?

The email header analyzer runs entirely in your browser: the headers you paste are never sent to us.

## An example

A cron job meant to run on weekdays fired on Saturday. You paste the expression into the cron tester, and the next-run list shows Saturday right there: the day-of-week field said 0-5 instead of 1-5 .

We also published an [HTTP status code reference](/docs/reference/http-status-codes) in the docs, with what each code means for monitoring and how to fix it. Every tool is listed under [Free tools](/free-tools).

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Canonical page: https://watchfor.io/changelog/2026-08-19-free-calculators-and-status-docs · Site guide: https://watchfor.io/llms.txt