Konvertera.nu
A conversion site for units and school data, in Swedish and English. New conversion pages are added daily without anyone writing them.
What it is
19 categories ship today: length, mass, volume, area, speed, temperature, time, pressure, energy, power, force, frequency, torque, voltage, resistance, capacitance, data storage, data rate and fuel consumption.
The site is bilingual, Swedish and English, through Polylang. Units and categories are keyed in English inside the engine while the URLs are localised, so the English page and the Swedish page are the same conversion rather than two implementations that can disagree.
The school section, Enhetsomvandling åk 4-9, carries its own promise: no ads, no login, no profiling or tracking of pupils, and no cookie banner. There is a separate page for teachers.
Every SI unit has a page of its own under /sv/si-systemet/: 15 in all, seven base units and eight derived ones.
How it is built
The conversion maths and the unit data are a Composer library of their own, konvertera/engine, with no WordPress in it at all. The site around it is Bedrock and Sage, deployed with Trellis, and everything that knows about routing, rendering and the embeddable widget sits in a separate mu-plugin. A unit definition is a fact about the world, so it lives outside the theme that renders it.
A unit’s name is not the unit. In Swedish, steg is a historical pace of 0.89 m and also what a pedometer counts, which is nearer 0.70-0.78 m. Fot is the Swedish foot of 0.296901 m and at the same time the international foot of 0.3048 m. Search demand for the modern meaning has twice been mistaken here for a signal to improve the historical unit’s page. That mistake does not produce a blank answer. It produces a confident wrong one.
The school pages quote a national curriculum, and a curriculum gets replaced. A page that keeps citing a superseded syllabus looks exactly like a page that is right. The curriculum text comes from Skolverket’s open syllabus APIs, which are CC0 and need no key, quoted with its SKOLFS provenance instead of retyped out of a PDF.
The origin runs on Trellis-provisioned Hetzner servers with Redis and an nginx FastCGI cache, behind Cloudflare with a four-hour edge cache on public pages.
What keeps it current
The engine’s data holds 9,030 conversion pairs. That is the real size of the job, and it is not a number of pages anyone writes by hand. What gets built one page at a time covers the pairs someone thought of, and no more.
A daily job adds up to 25 new conversion-pair pages per language, taken from a curated list of the ten most useful partner units for each unit. Nobody builds those pages.
A monthly job reads the site’s own Google Search Console data through a dedicated service account and folds it into each page’s internal ranking signal. What people actually search for reorders what the site puts forward, without an editor deciding it.
Every deploy regenerates a static, downloadable PDF for each category, unit and school page. On a school unit table there is a second path: a visitor can change the table through an allow-listed query string and download that version. That PDF is built on demand and streamed to the browser, never written to disk.