Platforms for developers

Real broken Linux servers in your browser: a process is filling the disk, Nginx will not start, a Kubernetes pod keeps crashing, and you have a few minutes to fix it. The closest thing to on-call practice you can get without a pager, with a free tier and a paid plan for the full set.

• DevOps
• Cloud

The Linux Foundation's platform for paid, structured mentorships on open source projects, including the cloud native projects run by CNCF. You apply to a specific project, complete any tasks the mentors set, and if selected you work on real issues with an experienced maintainer for a fixed term. It suits students and early career developers who want open source experience with guidance instead of guessing alone.

• Career
• Job search
• Cloud

Paid, remote three-month internships in open source and open science for people who face underrepresentation, systemic bias or discrimination in the technology industry of their country. Interns receive a $7,000 USD stipend. There are two cohorts a year, May to August and December to March, each with a short application window followed by a contribution period where applicants work on real project tasks with mentors.

• Career
• Job search

A yearly Google programme that pairs people new to open source with mentoring organisations for a paid, remote coding project. Contributors work for 12 weeks or more with a mentor and receive a stipend based on project size and country. Organisations are announced early in the year and the application window is short, so the real work is choosing a project and engaging with its community well before proposals open.

• Career
• Job search

Kaggle's public machine learning competitions, from beginner Getting Started and Playground contests to large prize competitions and hackathons. Your predictions are scored against a hidden test set, which quickly shows whether your validation is honest, and shared notebooks let you study how strong practitioners approach the same data. It suits students and engineers who want practice on real datasets with instant, objective feedback.

• AI
• Machine learning
• Programming

PortSwigger's Web Security Academy is a free online training platform with written lessons and hands-on labs where you exploit real vulnerabilities, from SQL injection, XSS and access control flaws to JWT attacks, API testing and attacks on LLM features. It is built by the team behind Burp Suite. It suits developers who want to write secure code and students aiming for security roles, because attacking a flaw yourself teaches prevention far better than reading a list of risks.

• Web
• Backend

One-to-one coaching with the author of the best-selling Grokking courses, a tech lead whose background spans Meta, Microsoft and Hulu, where he built and scaled distributed systems and data storage infrastructure. Sessions cover system design, data structures and algorithms, interview strategy and career direction. It suits engineers who have prepared seriously and want an expert read on what is still holding them back.

• Career
• Job search
• System design

Coding and system design coaching with Rafay Abbasi, a co-founder of the platform and former senior development lead at Microsoft (Azure Storage) and software engineer lead at Meta, where he built large-scale systems. Sessions focus on distributed systems, scalable architecture, data structures and algorithms, and interview strategy. It suits senior engineers who keep reaching onsite rounds without converting them, or whose designs stay at the level of boxes and arrows.

• Career
• Job search
• System design

A roster of interview coaches with backgrounds at companies such as Meta, Microsoft, Amazon, Snap, Cloudflare and Goldman Sachs, each bookable for coding, system design or broader interview and career coaching. You choose your coach from their profile rather than being assigned one. It suits candidates who want a coach matched to a specific company, level or weakness before a real interview loop.

• Career
• Job search

Live 60-minute mock interviews with engineers from large tech companies, covering system design, coding, behavioural rounds or a target company's format, with a verbal debrief and a prioritised list of fixes and drills. System design mocks are listed from $159, or $215 with an interviewer from your target company. It suits candidates with a real interview coming up who have never rehearsed under realistic, observed conditions.

• Career
• Job search
• System design

Free one-to-one sessions with Tauseef Fayyaz for approved Sefism members, booked from the Sefism dashboard: a 45-minute mentorship call, a 30-minute session for final-year students and new graduates, hour-long sessions on career guidance and personal branding, and a 45-minute LinkedIn optimisation session. It suits engineers stuck on a decision (which offer, whether to switch, what to learn next) and students planning their first job.

• Career
• Job search

A mentorship platform where experienced professionals in engineering, design, product, data and marketing offer one-to-one online sessions. ADPList says it has more than 36,000 mentors and 400,000 members across 160+ countries. Getting started now includes one free session. It suits students and early-career engineers who have never had a mentor and want an outside view on a career decision, a portfolio or job search.

• Career
• Job search

freeCodeCamp is a nonprofit that offers a free, browser-based coding curriculum with certifications, covering responsive web design, JavaScript, front end libraries, Python, relational databases and back end development. Its new Certified Full Stack Developer path adds exams and a capstone. There is no cost, no local setup and immediate feedback on every step. It suits complete beginners and anyone unsure whether they will enjoy programming, as the lowest barrier way to start.

• Web
• Programming
• Frontend

Frontend Mentor gives you professional designs and a written brief for 120+ real world front end and full stack projects across five difficulty levels, then lets you submit your solution for community and AI code review. Free challenges come with design images and one AI review a month; Pro adds Figma files, premium challenges and unlimited AI reviews. It solves the problem of not knowing what to build once tutorials run out.

• Web
• Frontend
• Programming

On-demand mock interviews with an AI interviewer for coding and system design rounds. It asks questions, follows up on your reasoning the way a real interviewer would, and ends with detailed feedback and a custom improvement plan. It suits software engineers preparing for technical interviews who want to practise whenever they are free and repeat sessions until their answers feel natural.

• AI
• Job search
• Career

The main public home for open machine learning models, datasets and demo apps, with more than three million models you can filter by task, library, licence and language. Each model has a card describing its training, intended use and limits, and many can be tried in the browser. It is essential once you need an open model because a hosted API is too costly, too slow or cannot receive your data.

• AI
• Machine learning

An interactive practice tool for system design questions: you work through a real-world design step by step on a whiteboard and receive AI-powered feedback on your answer. Your practice sessions are saved with their status, so you can return to them and review results. It fills the gap most preparation leaves open, which is actually producing designs under realistic conditions rather than only reading worked answers.

• System design
• Job search

A browsable practice library of coding problems that can be filtered by pattern, data structure, difficulty and company, so you can drill exactly the weakness you found this week. Patterns include two pointers, sliding window, hash maps, stacks, backtracking and greedy algorithms, with company filters for Google, Meta, Microsoft, Amazon, Oracle and LinkedIn. Free to browse, with an in-browser editor and solutions.

• Job search
• DSA

A public site, formerly LMArena and Chatbot Arena, where you ask a question, get two anonymous AI answers side by side and vote for the better one; votes feed public leaderboards. Free, quick practice for the side-by-side preference judgements at the heart of AI trainer work.

• AI

Google's dedicated bug bounty for security flaws in its AI products, launched in October 2025. It rewards issues such as rogue actions and sensitive data exfiltration, and explicitly excludes jailbreaks, direct prompt injection and content issues. Read its rules to learn what counts as an AI security bug and what does not.

• AI
• Career

TikTok's free creative hub for advertisers, now part of the TikTok One creative suite: Top Ads shows high-performing TikTok ads by industry with short notes on why they work, plus trends and creative tools. A free way to study hooks and pacing in short vertical video.

• Career
• Freelancing

Singapore's government-run job portal. Under the Fair Consideration Framework, employers applying for most Employment Passes must first advertise the job here for at least 14 consecutive days, with a clear salary range. That makes it a useful window into which Singapore employers are hiring and at what pay.

• Career
• Job search

The standard public leaderboard for embedding models, run by the open-source MTEB project. It scores models on retrieval, classification, clustering, reranking, semantic similarity and more, across many languages, so you can shortlist an embeddings model for search or RAG before testing it on your own queries.

• AI

A remote AI training platform where you qualify through a Starter Assessment for a track such as general writing, coding or STEM, then pick projects such as rating chatbot answers, writing responses and evaluating AI-generated code. Payment is through PayPal and the FAQ says it never asks workers for money.

• Career
• AI
• Freelancing