Guides
Practical notes on certificates, domains and charts. Every command was run before publishing, and every date and limit links to its primary source.
10 guides. Last updated .
Certificates and domains
How TLS certificates and domain registrations expire, how to check them, and what changes as lifetimes shrink.
-
47-day SSL certificates: timeline and prep
The CA/Browser Forum is cutting the maximum life of a public TLS certificate in three steps and shrinking how long a CA may reuse your domain validation. Here is the schedule, from the rules themselves, and what it asks of anyone who renews certificates.
Updated , 9 min read
-
Let’s Encrypt expiry emails ended: what now
For years, a failed Let’s Encrypt renewal came with a safety net: an email before the certificate ran out. That net is gone. Here is what changed, why, and how to replace it without adding another chore.
Updated , 7 min read
-
Check SSL expiry: openssl, curl, browser
Seven ways to read a certificate’s expiry date, from two clicks in a browser to a script that checks a list of hosts. Every command here was run before publishing, and the output shown is what it printed.
Updated , 10 min read
-
Fix “unable to get local issuer certificate”
Most certificate errors that show up in curl, Node.js or Python but not in a browser come from the chain. Here is how to read the chain a server sends, match each error to its cause, and fix it on nginx, Apache, Caddy and Cloudflare.
Updated , 9 min read
-
RDAP vs WHOIS: how to look up a domain
WHOIS answers in free-form text, over a protocol first published in 1982. RDAP answers in JSON over HTTPS, and for generic domains it is now the official source. Here is how to use it, and what to do when a TLD doesn’t support it yet.
Updated , 9 min read
Charts
Getting a chart into places where JavaScript can’t run: email, Slack, READMEs and PDFs.
-
Charts in email that actually render
A chart in an email is an image, whatever library drew it. Here is why, which image format and size to send, how to embed it, and how to keep it readable in dark mode and when images are blocked.
Updated , 8 min read
-
Send charts to Slack: n8n, Zapier and Make
There are three ways to get a chart into a Slack message: an image block pointing at a URL, an uploaded file, or Slack’s own chart block. Here is how each works, which one your automation tool supports, and the details that make images fail silently.
Updated , 7 min read
-
Chart.js to PNG: browser and server export
Exporting a Chart.js chart takes one line, and getting a good PNG takes five more. This guide covers both: the browser methods, the four things that spoil exports, and rendering charts on a server with no browser at all.
Updated , 6 min read
-
Charts in a GitHub README: images or Mermaid
GitHub renders no JavaScript in Markdown, but it does render images and Mermaid diagrams. Here is when to use each, how to make a chart follow the reader’s light or dark theme, and how to get a chart into a pull request comment.
Updated , 6 min read
-
Charts in PDFs: vector SVG or 300 DPI PNG
A chart in a PDF is either vector shapes, which stay sharp at any zoom, or a bitmap, which needs enough pixels for the page. Here is how to get the first, how to size the second, and why a canvas chart printed from a browser comes out blurry.
Updated , 7 min read