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Freelance React Native developerI ship apps that perform

React Native since it shipped in 2015. I help startups and scale-ups design, build and grow their mobile apps, from MVP to store release, all the way to fine-grained performance work.

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Portrait of Jérémy Magrin

80+engagements delivered

Available5.0 / 5

11 years

years of experience

80+

engagements delivered

5.0 / 5

freelance rating

500,000+

users across my apps

Trusted by

MWMOdisei MusicEpsorMistral AITwentySnoop MediaBetclic GroupCajooMon Spécialiste AutoCooknet (Cookomix)EDF Store & ForecastLuniNeliomon-marché.frZestBeJoe

How it goes

From an idea to an app your team owns

It starts with your idea

A workshop, specs, a scope. I say no to whatever does not need to exist in v1: that is what gets the app shipped.

The MVP ships in weeks

React Native and Expo, a base built to grow from the first commit. Lists, navigation, rendering: what gets expensive later is settled now.

Live on the App Store and Google Play

EAS builds, signing, store listings, over-the-air updates. And when a native API is missing from the ecosystem, I write the module myself, Expo or bare React Native, in Swift and Kotlin.

Or you arrive with an app that stutters

Lists that jank, a tab that freezes, a battery that melts. An inherited app, one that started badly, or one generated by AI: plenty of engagements begin here, not at step one.

A steady 120 fps, measured

At Odisei Music: a 40 to 50 % frame rate drop removed, CPU down 40 %, memory down 20 %. Before optimising, I measure.

120fps
40% CPU
20% memory

Your team takes over

Monorepo, shared design system, agentic tooling with guardrails, documentation. I leave when you no longer need me.

Recent work

What I have been building

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MWMMay 2026 → present

Software publishing

React Native developer

Design and build from scratch an Expo native module unifying MWM's Publishing and Advertising SDKs, making them available cross-platform for their clients.

React NativeExpo ModulesSwiftKotlinTypeScript

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Odisei MusicMay 2026 → present

Music / E-commerce

React Native developer - Performance specialist

Brought in as a React Native expert to optimise the mobile app's performance, with Android as the priority.

React NativeExpoPerformanceAndroidLegend List

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EpsorAug 2025 → May 2026

Banking & insurance

React Native developer

Design and roll out a web and mobile monorepo architecture, where the mobile app lived outside the existing monorepo and forced a package release for every shared change.

React NativeExpoNext.jsTurborepopnpm

View project

Mistral AIMar 2025 → Aug 2025

High Tech / AI · French unicorn

Mobile developer - React Native, iOS & Android

Grow the Le Chat mobile app with new flows and new native capabilities.

React NativeExpoSwiftKotliniOS

View project

TwentyJun 2023 → Mar 2025

Software publishing / Open source

Back-end and front-end developer - Nest.js, React.js

Build the back-end foundations of Twenty, the open-source CRM positioned as a modern, scalable alternative to Salesforce, with performance as a hard requirement.

Nest.jsGraphQLTypeScriptTypeORMReact.js

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Snoop MediaJan 2022 → Jun 2023

Social networks

Fractional CTO - React Native, Nest.js

Lay the full technical and organisational foundations of Snoop, a social network for film and series recommendations, as CTO as a service.

CTOReact NativeExpoNest.jsManagement

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Tech stack

The tools I reach for

My go-to stack is highlighted. The rest I bring in when the project calls for it.

Mobile

React NativeExpoEASTypeScriptExpo ModulesExpo RouterReact NavigationLegend List

Web

React.jsNext.jsTanStack QueryJotaiLegend StateZustandRedux ToolkitSolito

Back-end

Nest.jsPrismaPostgreSQLNode.jsGraphQLTypeORMDrizzleSupabaseFirebase

Native

SwiftKotlinModules natifsSDK iOS & AndroidObjective-C

Quality & delivery

CI/CDGitHub ActionsBunAgileTDDJestFastlaneRN Testing LibraryMaestroArgent
Open source

I publish and I contribute

Open source is a real part of how I work: I publish my own libraries and I contribute regularly to third-party projects, maintaining them, patching them and pushing fixes through.

@magrinj/expo-quick-look

github.com/magrinj/expo-quick-look

Expo native module for file preview: QuickLook on iOS, Intent chooser on Android. 100+ formats, native rendering rather than a WebView, authenticated remote downloads, iOS markup and multi-file navigation.

Expo ModulesSwiftKotlinTypeScriptBunpublié sur npm

@magrinj/parse-ingredients

github.com/magrinj/parse-ingredients

Multilingual recipe ingredient parser. Quantities, fractions and units parsed then aggregated, six languages supported, zero runtime dependencies.

TypeScriptBunpublié sur npm

Expo library in progress

A new Expo module in progress, opening up a native API that the Expo ecosystem does not cover yet.

Expo ModulesSwiftKotlin

Everything else lives on github.com/magrinj

I am a regular on the React Native conference circuit: App.js Conf in Kraków, and React Native Connection in Paris next.

Notes

What I write between projects

Field notes on React Native, mobile performance and native modules, from a freelance developer's daily work. Published on LinkedIn first, archived here.

34 746 communes de France dessinées par les habitants

de 1793 à aujourd'hui · Les villages restent sous l'eau · Les villes émergent comme des îles, puis deviennent des montagnes · Et Paris finit dans la neige · La même carte pour l'Allemagne tourne partout en ce moment · J'ai voulu la France, et remonter tout le…

Read the note

L'État a fait fuiter mon entreprise, Les Échos m'ont interviewé dessus

Une PME qui laisserait fuiter 678 000 dossiers serait déjà en liquidation · Lui s'excuse par mail et continue de nous facturer la RGPD · Il y a trois semaines je balançais un petit coup de gueule ici · La journaliste Joséphine Boone l'a lu, elle m'a appelé,…

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32% des boîtes ont arrêté d'acheter du logiciel cette année

41% dans la tech · Elles le codent elles-mêmes, McKinsey sort le chiffre et tout le monde applaudit la revanche sur le SaaS · Sauf que la moitié de ces boîtes va payer son outil deux fois · Le SaaS horizontal à l'abonnement, celui où tu payes 50 features pour…

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All notes

Client feedback

Rated 5.0 out of 5 on freelance platforms

Parfait en tous points ! Jérémy a un excellent niveau technique, un souci du détail particulier, s'est très rapidement investi dans le projet, et a été très apprécié de toute l'équipe.
Félix · Twenty
À l'aide de ses compétences en React Native, Jérémy nous a permis de faire un saut qualitatif dans la qualité du code de notre application mobile. Il connaît le framework y compris ses parties immergées, et sait faire preuve de pédagogie pour former ses pairs.
Lancelot Blondeel · CTO
Jérémy was very professional and autonomous. He really tried to understand the needs and pays a lot of attention to details. The work was delivered on time and exceeding expectations.
Zhou · Axens
Travailler avec Jérémy a été un plaisir. De par sa pédagogie et son expérience, il m'a beaucoup appris. Très rigoureux et minutieux pour toujours produire un code propre. Je ne peux que le recommander !
Roman Cirier · Développeur front-end
Excellent travail. Jérémy est intervenu pour lancer le développement de notre plateforme de demandes d'optimisation de prévision de consommation en énergies renouvelables, à destination du marché américain. Les chiffrages étaient précis et le code produit de qualité.
Yann Lombard · Responsable pôle front-end
Jérémy est un dev 5 étoiles : code de qualité, délais respectés, très réactif, il trouve toujours une solution aux problèmes posés. Vous pouvez lui faire confiance les yeux fermés.
Manu B · Chef de projet, Cooknet
Quelqu'un sur qui l'on peut toujours compter, disponible et force de proposition, même face à des problématiques complexes. Au-delà de la technique, une capacité d'adaptation rare qui lui permet de s'intégrer dans n'importe quelle équipe.
Valentin Martin · Head of Product, Allocab
Travailler avec Jérémy sur Snoop a été une expérience fantastique. Son expertise en React Native, GraphQL et NestJS a été cruciale pour le projet, et ses qualités humaines m'ont permis de me sentir valorisé à chaque étape.
Julian Mantet · Ingénieur fullstack, Snoop Media
Jérémy était responsable de l'architecture et des choix techniques de notre projet React Native. Son travail m'a permis d'avancer très vite sur les fonctionnalités, avec une expertise très appréciable dans un projet innovant.
Xavier Carpentier · Développeur React Native senior
Background

Eleven years, same curiosity

Other engagements

Betclic GroupJul 2021 → Dec 2021

React Native developer

Built and launched Betclic TV, an international mobile app rolled out in Portugal and Poland: sports news, live scores and match streaming.

CajooJan 2021 → Jun 2021

React Native, Nest.js developer

Strengthened the Cajoo delivery app, since acquired by Flink: in-app payment and new features.

Mon Spécialiste AutoJan 2020 → Dec 2020

React Native developer

Full offline-first rewrite of the mobile app, fully usable with no connection, to make field vehicle inspections reliable. Trained the mobile developers.

Cooknet (Cookomix)Jan 2019 → Dec 2020

React Native developer

Built and continuously grew Cookomix, a high-traffic recipe app used by more than 300,000 people every month.

EDF Store & ForecastSep 2019 → Dec 2019

React.js developer

Statistical analytics dashboard for end clients, making consumption data easier to read and track.

LuniJun 2019 → Dec 2019

React Native developer

Mobile apps for the Luni studio: group features on the Calendrier app in Swift and ReactiveSwift, then the Omada app in React Native.

NelioMar 2019 → Jun 2019

React Native developer

Optimised and extended the Nelio fresh-produce delivery app, on both performance and user experience.

mon-marché.frJul 2018 → Mar 2019

React Native developer

Built a white-label mobile app from scratch for home delivery of fresh produce. Clean, scalable architecture and fast MVP delivery.

ZestSep 2018 → Nov 2018

React Native developer

Supported ZestMeUp: trained the teams on clean React Native development and set up a solid technical base.

BeJoeFeb 2016 → Aug 2018

Mobile lead - React Native

Led the mobile side of BeJoe, a recommendations social network: technical foundations laid from day one of the company, mobile team management, iOS and Android apps.

Before going freelance · iOS developer in Swift and Objective-C on Timi, a business management platform, fully autonomous on the mobile side · Full-stack and mobile developer at Tack (BuzzVillage) in Node.js and Cordova · Django web developer for Les Libraires, turning a brochure site into an e-commerce store · Software developer at Thales Avionics in C and C++, on an automated verification tool for embedded widget libraries · Software developer at Thales Raytheon Systems in Java, C and C++, on the full migration of the SkyView programme.

Get in touch

Got a project in mind?

Guaranteed reply within the hour, plus a free thirty-minute video audit.

Email meMaltLinkedIn

Emailcontact@magrin.fr

Phone+33 6 73 12 19 30

Based inParis, France · fully remote