LectureAlly — Your AI professor for lecture slides
Upload your slides as a PDF. LectureAlly explains every slide out loud, follows along with word-synced captions, and answers your questions the moment they come up — the way a good tutor would.
Free · No account · Your slides stay in your browser
LectureAlly works with your own API key — Gemini, OpenAI, OpenRouter or any OpenAI-compatible endpoint, stored only in your browser. Get a free Gemini key or bring your own.
What LectureAlly does
It turns a silent PDF into a lecture you can actually listen to — and interrupt whenever something doesn't click.
Explains every slide out loud
An AI professor reads each slide, works out what it is actually saying, and narrates it in plain language — including diagrams and formulas, not just the bullet points.
Captions that follow along
Every narrated word is highlighted as it is spoken. Follow the text while you listen, or read ahead if the pace is too slow.
Ask questions mid-lecture
Stuck on a slide? Ask. The answer arrives in context, out loud, and the narration picks up exactly where your question interrupted it.
30 languages
Have German slides explained in English, or English slides in Spanish. The lecture language is yours to pick — useful when you study in a language that isn't your first.
Your slides stay in your browser
Nothing is uploaded to us. The PDF, the narration, the audio and your questions are cached in your own browser and never touch our storage. There is no account to create.
Export and pick up later
Save a finished lecture as a .lecture file with slides, narration, audio and Q&A inside, then drop it back in on any device to continue where you stopped.
How it works
Three steps, about a minute before the first slide starts talking.
Upload your slides
Drop in the PDF your lecturer handed out. Everything is read in the browser — there is no upload progress bar because there is no upload.
Pick the lecture language
Choose the language you want to be taught in. It doesn't have to match the language on the slides.
Press play and interrupt freely
The AI professor works through the deck slide by slide. Pause, rewind, or ask a question whenever something needs unpacking.
When students reach for it
Every one of these is the same problem: a slide deck that assumes you were there.
Revising for an exam
Go through 200 slides the way you'd go through a podcast — and stop to ask about the three that never made sense.
You missed the lecture
The slides are online, the recording isn't. Turn the PDF into the lecture you didn't get to sit through.
Studying in a second language
Have the slides explained in your first language, or the other way round when you need the technical terms in English.
Dead time on the train
Listen to a lecture the way you listen to anything else on a commute, at the gym, or while cooking.
Lectures in 30 languages
Pick the language you want to be taught in — independently of the language your slides are written in. Narration and captions both follow your choice.
- EnglishEnglish
- DeutschGerman
- FrançaisFrench
- EspañolSpanish
- ItalianoItalian
- العربيةArabic
- CatalàCatalan
- 中文Chinese
- HrvatskiCroatian
- ČeštinaCzech
- DanskDanish
- NederlandsDutch
- EestiEstonian
- SuomiFinnish
- ΕλληνικάGreek
- हिन्दीHindi
- MagyarHungarian
- Bahasa IndonesiaIndonesian
- 日本語Japanese
- 한국어Korean
- NorskNorwegian
- PolskiPolish
- PortuguêsPortuguese
- RomânăRomanian
- РусскийRussian
- SlovenčinaSlovak
- SvenskaSwedish
- TürkçeTurkish
- УкраїнськаUkrainian
- Tiếng ViệtVietnamese
The app interface itself is in English and German.
Frequently asked questions
The things people ask before their first upload.
Is LectureAlly free?
The app is free and there is nothing to sign up for. You do need your own API key for an AI provider, and you pay that provider directly for what you use. Google's Gemini has a free tier that is enough for normal studying.
Why do I need my own API key?
Because it is the only honest way to run a free tool that calls an expensive model. Your key is stored in your browser and sent only with your own requests: it passes through our relay to reach the provider, is never written down there, and there is no server-side key to run out.
Are my lecture slides uploaded anywhere?
Not to us. The PDF is opened and rendered in your browser and cached there. The slide currently being explained is sent to the AI provider you chose, because that is what generates the explanation, and narration text goes to Microsoft's speech service to be spoken. Nothing is stored on our servers.
Which files can I upload?
PDF slide decks, which is what almost every lecturer hands out. You can also re-open a .lecture file — LectureAlly's own export format, which packs the slides, narration, audio and Q&A into one file.
Which AI providers work with it?
Google Gemini, OpenAI, OpenRouter, and any endpoint that speaks the OpenAI chat-completions API — including most self-hosted and aggregator services. You pick the provider and the model in the settings dialog.
Can I ask questions while a lecture is playing?
Yes, and that is the point. Ask at any slide; the answer is generated with that slide in view, spoken out loud, and the narration resumes at the exact word your question interrupted.
Does it work on a phone?
Yes. The player is built for portrait phones, and rotating into landscape gives the slide the full screen. A whole deck lives in your phone's browser cache, so a lecture you have already generated keeps playing without regenerating anything.
Can I keep a lecture permanently?
Export it as a .lecture file. Browser caches get cleared — the export doesn't, and it can be re-opened on any device. That file is the permanent copy; the browser cache is just the working one.
Can it explain diagrams and formulas, not just text?
Each slide is sent as an image, so the model sees the layout, the diagrams and the notation the same way you do, rather than reading a stripped-out text layer.
Turn your next slide deck into a lecture
Upload a PDF and hear the first slide explained in under a minute. No account, no upload, nothing to install.
Upload your slides →