Built for ICPC-style programming contests, DOMjudge takes team submissions, judges them in a restricted sandbox, and posts a live scoreboard. Each team gets its own page. There they read the problem set, submit source code from the browser or a command line client, follow verdicts, and send clarification requests. Judges see every submission, judging run, and output diff. They verify results and rejudge a single submission or everything for a language, problem, team, or judgehost. Administrators schedule activation, start, freeze, end, and unfreeze times, import teams, categories, affiliations, and problems in bulk, and watch a traffic-light status for every team. The public scoreboard freezes for the final stretch and exports as a static HTML page. Judgehosts compile and run each solution with time and memory limits in languages such as C, C++, Java, Python, Kotlin, Go, and Haskell, with custom validators and interactive problems when a task calls for them. Balloon runners get a delivery queue. Clarifications sort into categories. Open contests accept self-registration. The Contest API and event feed connect external scoreboards, and a shadow mode compares results against another system. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. GPL-2.0 licensed.

Try an idea in React, Svelte, Python, or SQL without installing anything: LiveCodes is a browser-based playground where code compiles, runs, and previews the moment you type it. Starter templates open ready-made projects for most of the 90+ supported technologies. The desktop editor brings completion, multi-cursor editing, Emmet, and Vim or Emacs bindings, while a lighter touch-friendly editor takes over on phones and tablets. Packages from npm, deno.land/x, jsr, and GitHub import straight into your code, and a console, compiled-code viewer, and test runner show what happens behind the preview. Bring projects in from GitHub gists, GitLab snippets, JS Bin, or zip files, then share them as links or QR codes, export them as HTML, JSON, or zip archives, or send them to CodePen and JSFiddle. Deploy a project to a public URL on GitHub Pages, sync your work across devices, or broadcast your editor and result live to a classroom. An embed builder and SDKs for JavaScript, React, Vue, Svelte, Solid, Preact, and web components place playgrounds inside documentation pages, and prefilled code makes every example editable. Projects stay private by default. Local assets, snippets, themes, and dark or light modes tailor the workspace to each person. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

Describe an app in one sentence and sandboxd, a self-hosted AI app builder, has a coding agent build it in an isolated sandbox and hand back a live preview URL. Start from a blank prompt, a React, Next.js, Express, or FastAPI starter, or an imported public Git repo. Refine it in one persistent chat beside Preview, Code, Terminal, and Git tabs. Pick OpenCode, Pi, or Claude Code. Point OpenCode or Pi at local or remote OpenAI-compatible and Anthropic-compatible endpoints, LiteLLM gateways included. A proxy injects provider keys on the wire, so nothing secret lands in a sandbox. Did the agent get it wrong? Every task is checkpointed first, so one click reverts the turn. Snapshots, forks, and named versions keep known-good points to branch from. Edit files in the browser, review file-by-file diffs, commit, and push. Secrets are write-only and encrypted per app. Idle sandboxes sleep and wake on the next request. One modest server can host per-user previews, coding playgrounds, or an agent platform. The app library installs 80+ curated open-source apps, such as Ghost, n8n, Gitea, and Grafana, each in its own sandbox. Every console action is also a /v1 HTTP call with an OpenAPI spec. Upgrades back up the database, health-check the new version, and roll back on failure. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

CubeSandbox gives every AI agent its own hardware-isolated MicroVM with a dedicated Linux kernel — not a shared-kernel container but a true KVM virtual machine — booting in under 60ms with less than 5MB of memory overhead per instance, enabling thousands of concurrent sandboxes on a single server via kernel sharing and Copy-on-Write memory. The Rust-built CubeProxy exposes an E2B SDK-compatible REST API on Axum, so existing E2B Cloud applications switch by changing one environment variable with zero client code changes. CubeMaster orchestrates cluster-level scheduling in Go while Cubelet manages node-local sandbox lifecycles including create, run, pause, resume, snapshot, and destroy operations. CubeVS, the eBPF-powered network layer, enforces per-sandbox isolation with LPM trie-based egress policies entirely in kernel space — no userspace context switches — while CubeEgress provides an L7 security proxy with per-domain, per-path, and per-method allowlists plus automatic credential injection that keeps secrets invisible to sandbox code. Hundred-millisecond-granularity snapshots enable checkpoint, rollback, and parallel fork from any saved state. The volume framework supports E2B-compatible pluggable storage with independent lifecycle and cross-sandbox sharing. Production deployment uses Terraform on Tencent Cloud or Helm charts on Kubernetes, K3s, or TKE, with full ARM64 support alongside x86_64 and AutoPause/AutoResume for cost optimization. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. Apache 2.0 licensed.

Agent code needs somewhere disposable to run, and Sandstorm turns one modest VPS into a fleet of thousands of isolated sandboxes that wake the moment work arrives. You create sandboxes through a plain HTTP API, starting from a registered template or forking a tagged snapshot, with per-sandbox memory ceilings, attached volumes, and egress rules set on each call. Every sandbox is a gVisor container with its own network namespace, so untrusted agent code runs away from your host and away from its neighbors. Idle sandboxes cool down through four tiers, from running hot, to frozen in place with a wake time near ten milliseconds, to checkpointed on disk and back in about a fifth of a second, so a small machine can hold far more sandboxes than it could ever keep running at once. A single binary acts as master, node, and web console: the master tracks desired state and places work across nodes, nodes behind NAT dial out to join the fleet, and a gateway on each node wakes a sleeping sandbox and forwards its traffic automatically. The built-in Hub pulls ready-made snapshot packs for warmed runtimes like Python with numpy or a pre-warmed Playwright browser, skipping cold starts entirely. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. Apache-2.0 licensed.

Containarium gives every AI agent a persistent Linux box of its own, reachable over SSH and driven through structured tools instead of a fragile terminal session. One command creates a named sandbox, syncs the SSH configuration, and wires the box into Claude Code, Codex, Gemini or Cursor through an MCP server that runs inside the container. From there the agent can execute shell commands, read and write files, install services, and expose a port on a public hostname with TLS terminated by a Caddy sentinel. Detached code runs keep working after a laptop sleeps or a connection drops, and the operator reattaches to the same byte-exact log later, checks status, or stops the run without losing output. An optional per-tenant eBPF egress policy limits outbound traffic per box, logs denied attempts for audit, and keeps provider API keys inside a model gateway rather than inside the agent environment. Boxes run on LXC or Kubernetes, keep state between agent sessions, support GPU passthrough for local model work, and stay separate from the host operating system and the cluster control plane. The dashboard presents containers, traffic, security events, audit records, GPU state and monitoring in one place. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. Apache-2.0 licensed.

Microcks turns your API specifications into living mocks and contract tests, so teams can develop and verify against an API long before the real implementation exists. Feed it OpenAPI, AsyncAPI, GraphQL schemas, gRPC Protobuf files, Postman collections, or SoapUI projects, and it immediately publishes mock endpoints that answer with realistic examples drawn from the specification itself. Dispatching rules route requests by path, query parameters, headers, body content, or XPath and Groovy expressions, while content negotiation and templating functions shape each response to look convincingly real. Event-driven APIs get the same treatment, with AsyncAPI mocks that publish messages to Kafka topics or WebSocket channels your consumers can subscribe to during development. When an implementation shows up, contract tests replay the recorded expectations against the live service and report every mismatch, down to the exact request and response that failed. Run those tests from the web interface, on a schedule, or from CI pipelines with the command-line client, and wire importers to rescan your Git repositories so new specification versions appear as mocks automatically. The built-in hub adds one-click samples and reusable API packages, giving a new team a stocked repository of mockable services within minutes of the first login. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. Apache-2.0 licensed.

Exploratory data work, teaching material, and research code all live in the same browser tab with JupyterLab, the web workspace of Project Jupyter. Notebooks combine runnable code cells, Markdown, and rich output such as images, JSON, and Vega charts, and they use the same notebook format as the classic Jupyter Notebook. Any Jupyter kernel can execute the code, so Python, R, and other languages share one interface, and code inside plain text files such as Markdown or LaTeX can be run interactively as well. Tabs and splitters arrange documents side by side, and a notebook's cell outputs can be mirrored into their own tab to build a simple dashboard with interactive controls. Code consoles serve as scratchpads linked to a notebook kernel, while full terminals run system shells such as bash on the server. A visual debugger offers breakpoints, a call stack, and a variable explorer for kernels that support the Jupyter debug protocol. Markdown, CSV, and Vega documents show a live preview as they are edited, and built-in viewers handle images, JSON, and PDF files. The Extension Manager installs themes, editors, and renderers from PyPI, and real-time collaboration becomes available by adding the jupyter-collaboration extension. Access is protected by a generated token unless a password is set. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. BSD-3-Clause licensed.

One server, a login for everyone, and a private JupyterLab in every browser tab: that is the whole pitch, and for classrooms and research teams it is transformative. JupyterHub authenticates each user against your existing identity system (campus OAuth, GitHub, Google, LDAP, or local accounts), then spawns a dedicated single-user server just for them, with their files, their kernels, and their compute allocation. Users open notebooks, terminals, and extensions in JupyterLab without installing anything, and their environment is identical whether they log in from a lab workstation or a laptop at home. The Spawner decides where those servers live: plain processes on one machine for a small class, Docker containers for isolation, or Kubernetes pods that scale across a cluster for a whole university. Administrators manage users, groups, and named servers from the admin panel, grant precise permissions through roles and scopes, and watch start times and profiles for every running server. External services plug into the Hub API, so dashboards, autograders, and portals can authenticate through the same OAuth machinery. When a user disappears for the semester break, culling stops their idle server and frees the resources. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. BSD-3-Clause licensed.

Eclipse Che spins up complete development environments on Kubernetes from a Devfile in the project repository, so new developers click a factory link and open a browser IDE with dependencies, runtimes, and debugging already configured instead of spending their first day installing toolchains. Each workspace runs as a DevWorkspace custom resource in the user's namespace, making environments API-manageable with kubectl and GitOps tooling alike. Developers choose their editor per workspace, from Visual Studio Code Open Source to JetBrains IDEs via Projector, and the 7.124 release adds Orca, an agent development environment for working alongside AI coding agents. Workspaces carry their own containers for build and run, so code executes in a production-like environment with direct Kubernetes API access from the IDE. Teams standardize stacks as Devfile templates, onboard contributors in minutes, and open a fresh workspace per branch or pull request in a new browser tab. The 7.124 release also builds workspace lifecycle commands into chectl, including SSH connections with port forwarding to desktop editors, and DevWorkspace Operator 1.0 adds optional per-workspace NetworkPolicy isolation. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. EPL-2.0 licensed.

With over 14,000 GitHub stars and enterprise adoption by security-conscious organizations, Coder transforms how development teams provision, manage, and secure their coding environments. Every workspace is defined as a Terraform template, meaning infrastructure engineers can standardize development environments across EC2 instances, Kubernetes pods, Docker containers, or any combination, while developers get self-service provisioning that launches in seconds rather than days of manual setup. The WireGuard-based networking layer establishes encrypted tunnels between developer machines and remote workspaces, providing low-latency access without exposing ports or configuring VPN concentrators. Automatic idle detection shuts down unused workspaces after configurable periods, directly reducing cloud compute costs for organizations running hundreds of developer environments. The Coder Agents feature introduces native AI coding capabilities where the agent loop executes entirely within the control plane on self-hosted infrastructure, keeping LLM API credentials out of individual workspaces and eliminating credential exfiltration risks. Centralized model governance allows platform teams to approve specific AI providers and models, set per-user spend limits, and maintain complete audit logs of all prompts, tool calls, and agent activity. IDE integration supports VS Code through a dedicated extension, JetBrains IDEs via Gateway and Toolbox plugins, and browser-based code-server for web access. The template registry provides pre-built configurations for common development stacks. DevContainer support builds environments from standard devcontainer.json specifications. Deploy on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL-3.0 licensed.

With over 78,000 GitHub stars, 270 contributors, and seven years of continuous development tracking upstream VS Code releases within days, code-server has become the definitive way to run a full Visual Studio Code IDE on any remote machine and access it from any browser on any device. The project applies a curated set of patches to Microsoft's VS Code codebase that add password authentication, sub-path hosting behind reverse proxies, self-contained web views that never call out to Microsoft servers, a built-in proxy for accessing ports on the remote machine directly through the VS Code ports panel, and on-disk settings persistence instead of browser storage. The extension ecosystem works with the Open VSX marketplace by default, giving access to thousands of extensions for Python, JavaScript, Go, Rust, Java, and every other language, along with themes, linters, formatters, and debuggers. The integrated terminal provides direct shell access to the server, Git integration handles version control without leaving the editor, and the debugger supports breakpoints, variable inspection, and step-through execution for Node.js, Python, Go, and other runtimes. DevContainer support enables reproducible development environments defined in JSON configuration files. Installation options include a one-line install script, manual package installation, Docker via the official codercom/code-server image, and DevContainer features. Minimum requirements are a Linux machine with 1GB RAM, 2 vCPUs, and WebSocket support. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

Share a game, a film, or your holiday photos with up to 20 friends, and let them watch from a browser tab with nothing to install. The host picks a screen, window, browser tab, or camera, then sends an invite link or a four-digit room code, with an optional room password. Friends open it on a desktop or phone, press Play, and chat or react while it runs, with optional on-screen chat. A microphone switch adds spoken commentary, with a choice of input device and voice volume. Video travels directly between participants where possible, and a self-hosted server can add automatic forwarding for networks that block direct links. Sharing settings cap resolution from 480p to 1440p, frame rate up to 60 fps, and audio at 64, 128, or 192 kbps, with Clarity, Balanced, and Fluency presets and a choice of VP8, H264, or automatic codecs. Viewers get playback controls, picture-in-picture, fullscreen, light and dark themes, and a connection topology view. The interface follows the system language in Chinese or English, with a visual-only mode for a text-free look. Piik App adds native capture on Windows, macOS, and Linux, while a hosted site works from any desktop browser. A self-hosted site can set a site passphrase, a viewer limit per room, and automatic cleanup of empty rooms. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

Starred by over 6,500 users on GitHub and trusted by organizations including Toyota, CTFd has been the leading open-source platform for hosting cybersecurity competitions since 2015, providing everything needed to run professional Capture The Flag events through a clean web-based administration panel without touching a database query. The framework supports both individual and team-based competitions with automatic tie resolution, configurable score freezing, and scoregraphs comparing the top teams with detailed progress tracking. Challenge creation offers static and regex-based flags, dynamic scoring that adjusts point values based on solve count, unlockable hints purchasable with points, file attachments uploaded to local storage or Amazon S3-compatible backends, and challenge attempt limits with automatic bruteforce protection. Version 3.8 introduced challenge logic fields controlling flag submission behavior with any, all, and team modes, integrated dynamic scoring into the standard challenge type, participant ratings and reviews on challenges, and admin-stored challenge solutions viewable after competition. The Markdown-based content management system enables custom pages for rules, FAQs, and resources, while SMTP and Mailgun integration handles email confirmation and password recovery. The plugin architecture supports custom challenge types, flag validators, and scoring algorithms, while the theme system provides complete visual customization. Import and export functionality preserves entire competition configurations for archival and reuse across events. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. Apache 2.0 licensed.