Open source · MIT

Type what to show. Get the demo video.

jev-demofast drives your real product in a browser, outlines every element it uses, and renders the MP4. Every step is decided by Jev, a fast decision model, in about a quarter of a second.

Get demos made for you Run it yourself →

~0.25 sper decision

18–31 ssentence to narrated video

centsper demo

~/saas-starter — a real run

$jev-demofast index ./saas-starter --out app-index.json mapped 8 routes, 42 links from source $jev-demofast demo "Sign in as test@test.com with password {{PASSWORD}}, then invite jane@example.com to my team as a member." --url http://localhost:3000/sign-in --index app-index.json --voice thalia jev /sign-in: the form is here 0.97 303 ms jev submit Sign in 231 ms jev /dashboard: the invite form is here 0.86 210 ms jev submit Invite Member 297 ms jev done? yes, 0.82 215 ms narrating: script, voice, music invite.mp4: 27 s, ready 18.3 s after the sentence

How it works

What happens between the sentence and the video

Map optional · from code

Point it at your repo. It reads every route, link, form and button from source, so on your app it knows where each click leads before it clicks.

Drive Jev

On each screen Jev answers one question: is the goal done, is its form here, or is it somewhere else? It acts only when it is at least 50% sure, and never signs up, logs out or deletes.

Record ffmpeg

Outlined frames, typed values blurred if you like, passwords never shown to a model, and an MP4 or GIF out the other end. Add --voice for a narrator.

Early access

Two ways to use it

Free · MIT

Run it yourself

The whole tool is open source. Bring your own Cloudflare account; a demo costs cents to make.

Any website, or your own app with a map built from its source
Narration, voice, music and dry runs included

Prefer we handle it? Send your product and the flows you want shown. We deliver narrated demo videos on your staging site, and re-record them when your product changes. Voice, pace and music to fit your brand; nothing touches production. Coming next: hosted, so demos re-record themselves on every release.

Early access · request an invite

Get early access

Quickstart

Run it on your own app

Four steps, about five minutes. Everything runs on your machine; only the model calls go to your Cloudflare account.

Install

git clone https://github.com/q3learners/jev-demofast
cd jev-demofast && uv sync
export CLOUDFLARE_ACCOUNT_ID=...  CLOUDFLARE_API_TOKEN=...

Start its browser

A separate Chrome profile, so your own browser and logins stay untouched. Add --open with your login page to sign in once; the profile remembers it.
```
uv run jev-demofast chrome
```

Describe the demo

An LLM sketches the route once; Jev picks every click on the live page.

uv run jev-demofast demo "Show how to find trending projects on GitHub this week" \
    --url https://github.com/ --out trending.mp4 --gif

Map your app from its source in about a second, then Jev drives from the map with no route plan. Passwords stay a {{PASSWORD}} placeholder and are typed straight into the field.

uv run jev-demofast index ../my-app --out app-index.json
DEMO_PASSWORD=... uv run jev-demofast demo \
    "Sign in as test@example.com with password {{PASSWORD}}, then invite jane@example.com" \
    --url http://localhost:3000/sign-in --index app-index.json --out invite.mp4

Make it presentable

Add any of these to the demo command:

--voice thalia
a narrator, with a script written from what was on screen

--voice-speed 1.2
a little faster, same pitch

--music track.mp3
a music bed that dips under the voice (use a track you have the rights to)

--dry-run
stop right before anything that would change data