Measuring professor emphasis, live

Stop studying everything.
Study what gets tested.

Nocturne links your lecture audio, slides, and study guide — then surfaces the Red Zone: the handful of keywords your professor actually emphasized, ranked by how likely they are to appear on the exam.

Request beta access →See how it works →

Zero-knowledge encrypted  ·  Runs in your browser  ·  No credit card required

Built for high-stakes fields

Pre-medMedical schoolNursingPharmacologyEngineeringBuilt for all STEM programs — anywhere a single lecture can carry the examComputer ScienceOrganic ChemistryPhysicsBiochemistryLawGraduate STEMPhD programs

The problem

A lecture is mostly noise.

Fifty minutes of talking. Three slides that actually matter. Somewhere in the transcript are the four phrases that carry the exam — and you're meant to find them by re-reading everything.

Professor emphasis · one lecture

TalkingTested
00:0050:00
4phrases decide the grade
≈ 8,400 words spoken · the rest is noise

How it works

Works with whatever you have.

01Slides only

Start with your deck

Nocturne extracts text from every slide and generates a Synthetic Study Guide automatically. Likely Zone keywords appear immediately.

PDF viewerSynthetic guideFlashcards
02Add a recording

Layer in the lecture

Whisper transcribes your audio in-browser. The silence-gap engine syncs each word to its slide, measuring dwell time per topic.

Word-level syncEmphasis detectionConfidence
03Full session

Surface the Red Zone

Cross-reference your study guide against what the professor emphasized. Red Zone keywords are scored, hot-linked, and exported.

Red Zone scoringHeatmapAnki export

The Red Zone, live

Watch it surface what matters.

Add what you have, and Nocturne sharpens its read. Step through a real lecture moment below.

Lecture transcript

“This is absolutely fair game for the midterm. The electron transport chain is where most of your net ATP yield actually comes from — not glycolysis. Know substrate-level phosphorylation cold, and remember pyruvate is the hand-off into the Krebs cycle.”

Surfaced keywords

3 Red · 2 Likely

Cross-referenced against your study guide. These are exam-critical.

electron transport chain94%
Red Zone
substrate-level phosphorylation88%
Red Zone
net ATP yield83%
Red Zone
glycolysis72%
Likely Zone
pyruvate60%
Likely Zone
Export 3 Red Zone flashcards → .apkg

What's inside

Everything the serious student needs.

Red Zone Detection

AI-powered Red Zone Detection cross-references your study guide against slide density and verbal repetition to surface the highest-yield keywords.

Emphasis Detection

Measures how long the professor dwells on each slide and how often they repeat each term. Not what was said — what was stressed.

Confidence Score

Each Red Zone keyword gets a per-keyword score derived from slide density, verbal mentions, and study-guide alignment.

Anki Integration

Import your existing deck to seed the guide. Export Red Zone cards as a valid .apkg, tagged and ready for spaced repetition.

Zero-Knowledge Encrypted

Files are AES-GCM encrypted in the browser before upload. The server stores opaque blobs it cannot read.

Runs in Your Browser

Whisper and BERT run as WASM Web Workers on your device. No audio leaves your machine on the free tier.

Why it's different

A note-taker records. Nocturne ranks.

Otter, Notion, and Turbo hand you notes and flashcards to grind through. Nocturne tells you which terms matter — ranked by how likely each one is to be on the exam.

Otter.ai
Notion AI
Turbo AI
Nocturne
Transcribes the lecture
✓
—
✓
✓
Auto-generates notes & summaries
✓
✓
✓
✓
Makes flashcards & practice quizzes
—
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✓
✓
Measures what the professor emphasized
—
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✓
Ranks every term by exam likelihood
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✓
Cross-references your own study guide
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✓
Slide-dwell + verbal-repetition heatmap
—
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✓
Audio never leaves your device
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✓
Exports a valid, tagged Anki .apkg
—
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✓

Zero-knowledge architecture

The server stores data it cannot read.

Nocturne's encryption isn't a marketing claim — it's a structural constraint. Your vault passphrase derives the key that wraps your Master Key, and that passphrase never leaves your browser.

  • Vault passphrase never leaves your device — not even hashed
  • Master Key is non-extractable; created with extractable: false
  • Files are AES-GCM 256 encrypted before upload
  • PBKDF2 at 310,000 iterations runs in a Web Worker, off the main thread
  • Whisper + BERT run locally via WASM — nothing leaves the browser on Free
  • No password reset exists. There is no backdoor.

3-Tier key hierarchy

Passphrase
your memory only
PBKDF2 · 310,000 iterations · SHA-256
KEK
memory only, discarded after unwrap
AES-KW unwrap
Master Key
non-extractable CryptoKey
AES-GCM 256 · unique IV per file
Encrypted .bin blob
stored in Supabase — opaque to the server
No password reset exists. There is no backdoor.

Pricing

The free tier is the full product.

The complete core pipeline is free. Paid tiers add sharper ASR and more storage — never access to the basics.

Billed annually · three months free vs. paying monthly

Dusk
$0forever
Free forever — no card needed

The full core product.

Request beta access
  • ✓PDF viewer + slide extraction
  • ✓Whisper browser transcription
  • ✓Synthetic Study Guide
  • ✓Red Zone scoring
  • ✓Slide density heatmap
  • ✓Anki .apkg import + export
  • ✓500 MB encrypted storage
  • ✓3 sessions per month
MidnightPopular
$8$6/mo
$72 billed yearlySave $24/yr

Sharper transcription. More storage.

Request beta access
  • ✓Everything in Dusk
  • ✓Server-side ASR + diarization
  • ✓Hotword injection from guide
  • ✓YouTube Red Zone search
  • ✓Cross-session convergence
  • ✓Exam Urgency Mode
  • ✓5 GB encrypted storage
  • ✓Unlimited sessions
Eclipse
$20$15/mo
$180 billed yearlySave $60/yr

Everything, with AI explanations.

Request beta access
  • ✓Everything in Midnight
  • ✓AI summarization (opt-in)
  • ✓Practice quiz mode
  • ✓Cross-session deck merging
  • ✓Markdown notes export
  • ✓20 GB encrypted storage
  • ✓Priority processing

Questions

Good to know.

No. Nocturne generates a Synthetic Study Guide from your slide text alone, so Likely Zone keywords appear before you upload anything else.

On the Free tier, never. Whisper runs as a WASM Web Worker directly in your browser — no audio is uploaded. Server-side ASR is opt-in on paid tiers.

The handful of keywords your professor most emphasized — measured by slide dwell time and verbal repetition, then cross-referenced against your study guide and ranked by exam likelihood.

Your passphrase derives a key that wraps a non-extractable Master Key. Files are AES-GCM 256 encrypted in-browser before upload. The server only ever stores opaque blobs.

It is the full core product: transcription, Red Zone scoring, heatmaps, and Anki export — capped at 3 sessions per month and 500 MB of storage.

Yes. Import any .apkg and your card fronts seed the study guide automatically. Export Red Zone cards back out as a valid, tagged .apkg.

Closed beta

Request early access.

We're onboarding a small cohort of students. Tell us a bit about yourself and we'll reach out with an invite code.

We'll only use your email to send the invite code and occasional beta updates.

Walk into the exam
knowing what's on it.

Apply for early access — we're onboarding a small cohort of students before the public launch.

Request beta access →See what's included