About Martin

TypeScript expert, focused on how fast the type checker runs and how much you can trust what it says.

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Portrait of Martin Ferret
Martin Ferret France, working remotely across Europe

I work on how fast TypeScript checks types. I build small experiments that isolate one cause of slowness, measure it on TypeScript 6 and 7, and publish the result with the raw numbers, including when the hypothesis turns out to be wrong.

When the cause sits in TypeScript’s own type definitions, I try to fix it there. My first pull request to the DOM type definitions was merged in November 2026. I also spend time on open issues: reproducing reports, checking edge cases and proposing an approach before anyone writes code.

I’m Lead Content Owner for the JavaScript and TypeScript certifications at Certificates.dev, and I run What's up TypeScript France, a free online meetup in French.

Method

How I work

The same loop for every slowdown, from the first measurement to the published result.

  1. Step 1

    Measure

    Run tsc with extended diagnostics on a real project and record check time, memory and instantiations.

  2. Step 2

    Isolate

    Shrink the slowdown to one cause in a small experiment, with a safety file proving the types stay as strict.

  3. Step 3

    Fix upstream

    When the cause lives in TypeScript’s own types, open a pull request there, not a workaround.

  4. Step 4

    Publish

    Ship the raw numbers and the machine they ran on, whatever the verdict.

TimelineEvery contribution, talk and experiment, by dateEach entry links to its source.Open the timeline

Contact: mferret.pro@gmail.com. For a talk, a workshop or a podcast, see Invite me.