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Flems

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What Flems is

Flems is a free, open-source browser playground for prototyping and sharing front-end examples. It is a static web application that runs in the browser, with web and self-hosted deployment options. A new playground starts with HTML, JavaScript, and CSS files, and users can add more files. Code executes after the page loads in an iframe runtime, with an editor, runtime console, and automatic reload. Flems supports TypeScript, LiveScript, and Babel standalone compilation. CSS and JavaScript dependencies can be added by URL or NPM package reference and are fetched from unpkg.com. Playground state is compressed into the URL hash, so the link can reopen the current example. The open-source module can be embedded or self-hosted and exposes controls for toolbar, file tabs, link tabs, sharing, reload, and console visibility. CORS-enabled linked files shorter than 200,000 characters open in the editor; other linked files remain links. Fullscreen is disabled. The repository identifies the WTFPL license.

Who it suits

Flems suits developers who want a lightweight browser workspace for front-end prototypes and shareable examples. Its self-hosting and embedding options also fit projects needing an open-source module.

What it does well

  • Free and open source
  • Runs code in an iframe browser runtime
  • Supports TypeScript, LiveScript, and Babel
  • Shares playgrounds through URL state
  • Can be self-hosted or embedded

What to know first

  • It is a static, not full-stack, runtime
  • Fullscreen functionality is disabled
  • Long linked files may remain external links
  • Dependencies are fetched from unpkg.com

Verdict

Flems focuses on quick front-end experimentation, browser execution, and link-based sharing. Its static runtime and linked-file limits make it less suited to full-stack development or unrestricted file editing.

Facts from Flems's own pages

Browser execution
After the page loads, code is computed in the browser and saved as a compressed string in the URL. · github.com, 12 Oct 2026
Compilers
The site README says Flems supports TypeScript, LiveScript, and Babel standalone compilation. · github.com, 12 Oct 2026
Default files
A new Flems starts with HTML, JavaScript, and CSS files, and users can add more files. · github.com, 12 Oct 2026
Dependencies
Users can add CSS and JavaScript dependencies by URL or NPM package reference, which are fetched from unpkg.com. · github.com, 12 Oct 2026
Deployment options
static · flems.io, 24 Sept 2026
Editor and runtime
The module README lists an editor, runtime console, automatic reload, and controls for toolbar and file tabs. · github.com, 12 Oct 2026
Editor options
The Flems module exposes options to show or hide the toolbar, file tabs, link tabs, share and reload buttons, and console. · github.com, 12 Oct 2026
Embed and self-host
Flems.io is based on an open-source Flems module that can be used for self-hosting or embedding. · github.com, 12 Oct 2026
Files and languages
A new Flems starts with HTML, JavaScript, and CSS files, and it supports TypeScript, LiveScript, and Babel standalone compilation. · github.com, 12 Oct 2026
Fullscreen limit
The Flems.io README says fullscreen functionality is currently disabled. · github.com, 12 Oct 2026
Full-stack runtime
No · flems.io, 24 Sept 2026
Integration limit
For linked files, the module README says CORS-enabled files shorter than 200,000 characters open in the editor; other linked files are simply linked. · github.com, 12 Oct 2026
License
The Flems repository identifies its license as WTFPL. · github.com, 12 Oct 2026
Limit
The project README describes Flems as a static web app and browser code playground. · github.com, 12 Oct 2026
Product
Flems describes itself as a browser coding playground. · flems.io, 12 Oct 2026
Purpose
Flems is a browser playground for prototyping and sharing front-end examples. · github.com, 12 Oct 2026
Runtime
The module uses an iframe as a runtime for the code being edited. · github.com, 12 Oct 2026
Self-hosting and embedding
Flems.io is based on an open-source Flems module that can be self-hosted or embedded. · github.com, 12 Oct 2026
Shareable links
Flems stores application state in the URL hash, so the URL can link to the current playground state. · github.com, 12 Oct 2026
Sharing controls
link_access · flems.io, 24 Sept 2026
Sharing
Flems stores playground state as a compressed string in the URL, which serves as a shareable link to the current example. · github.com, 12 Oct 2026
Support
The module README directs users who need bundling help to create an issue. · github.com, 12 Oct 2026
Use case
Flems.io is described as a web playground for prototyping ideas and sharing working front-end code examples. · github.com, 12 Oct 2026

Where Flems stands on Freedom251

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