Local · No uploads

Audio trimmer with fades

Mobile·FullDesktop·Full

Edit

Cut a clip to a start/end range and add fade-in / fade-out — all in your browser with FFmpeg.

Mobile·FullDesktop·Full

Your audio stays on this device

FFmpeg and the Web Audio API run in your browser. Files are processed in a Web Worker and are never uploaded.

Input

Processed locally with FFmpeg in a Web Worker

Drop an audio file or tap to choose

MP3, WAV, FLAC, OGG, M4A · stays on your device

Result

Run the tool to produce output audio you can preview and download.

There is no upload endpoint — your files are processed in this browser tab. Open your network tab and check. See how it stays private.

How to trim audio

  1. Add the audio. Drop an MP3, WAV, or other audio file onto the tool or browse for it.
  2. Set the range. Choose the start and end of the segment you want to keep.
  3. Add fades. Optionally fade the start and end in and out for a clean edit.
  4. Download. Export the trimmed clip locally and save it.

Trimming audio is the everyday task behind ringtones, podcast pickups, and pulling a clean sample out of a long recording. Doing it locally keeps interviews, voice notes, and unreleased tracks off any server.

Set the in and out points, then add short fades so the clip starts and ends without an abrupt click. The cut is precise, and you control the export format to trade file size against fidelity.

To even out loudness across a clip, use Normalize; to strip vocals for a backing track, use the Vocal remover; and to switch formats, use the Format converter.

Frequently asked questions

Can I use this as an MP3 cutter?

Yes. Load an MP3, set the range, and export just that part — a ringtone, a sample, or the good take from a long recording.

Do fades change the whole track?

No. Fades apply only to the start and end of your selected segment, easing it in and out without touching the middle.

Will trimming reduce audio quality?

Trimming itself does not degrade the audio; exporting to a lossy format re-encodes it, so choose WAV or a high bitrate to preserve fidelity.

Is my audio uploaded to trim it?

No. The clip is processed in your browser tab; the file's bytes never leave your device.

Related tools

Audio Lab tools

All processing stays in your browser

Technical transparency

SafePaper is built so your PDFs are processed in your browser, not on SafePaper servers. The sections below explain this in plain language.

Hosting & delivery

  • The site is a Next.js (App Router) application. Production is static HTML, JavaScript bundles, CSS, and assets—served like any modern front-end (e.g. on Vercel).
  • There is no Route Handler, no pages/api, and no server action that accepts your PDF for processing. We do not operate an upload endpoint for document bodies.

Runtime (your machine)

  • UI is React 19 + TypeScript, styled with Tailwind CSS, with motion via Framer Motion where noted in the interface.
  • Dropped files are read with the browser File API into ArrayBuffer / Uint8Array and kept in client-side React state (a shared provider across tool pages in one visit). The visible queue is also mirrored to sessionStorage when it fits browser limits so a refresh in the same tab can restore filenames and bytes without contacting a server.
  • Heavy merge, split, organize, compress, crop (CropBox and multi-region PDF exports), and redact PDF output runs in a dedicated Web Worker (pdf-operations.worker.ts, compress-pdf.worker.ts, bookmarks-outline.worker.ts, extract-embedded-images.worker.ts, crop-pdf.worker.ts) so the main UI thread stays responsive. Buffers are passed with postMessage + Transferable where supported to avoid extra copies.
  • Organize's optional duplicate-page scan runs in pdf-duplicate-pages.worker.ts with pdf.js + OffscreenCanvas—still only on your device.

Security Vault

  • Security Vault (/security) runs JWT decode, hashing, AES file encrypt, key generation, TOTP, bcrypt, and Shamir sharing with Web Crypto and jose in your tab only.
  • Optional site analytics and the consent banner are disabled on Security Vault routes even if you opted in elsewhere—so secrets pasted here are not on pages that load Vercel Analytics.

Share Desk (peer-to-peer)

  • Share Desk (/share) transfers files with WebRTC data channels directly between two browsers. SafePaper does not store or process file bytes on our infrastructure.
  • A separate WebSocket signaling service (configured via NEXT_PUBLIC_SIGNALING_URL) relays SDP offers/answers and ICE candidates so peers can find each other. That relay carries connection metadata only—not your file contents.
  • Large receives stream into OPFS via opfs-writer.worker.ts so the main UI thread stays responsive. Senders read files in 64KB slices with data-channel backpressure.
  • Peers may use Google's public STUN (stun:stun.l.google.com:19302) to discover network paths. Optional TURN env vars (NEXT_PUBLIC_TURN_URL, etc.) can relay traffic on restrictive networks—that is separate third-party network traffic, not a SafePaper file upload.

PDF stack

  • Structural PDF work (merge order, page extraction, rotation, removal) runs in the worker path described above.
  • Optional password protection applies AES-256 encryption on the main thread after the worker returns bytes, using the browser's Web Crypto API. Your open password is not sent to any server.
  • Previews and raster export (PNG images and plain-text extraction) use a canvas-based PDF renderer in a separate worker. The preview worker script is served as static /pdf.worker.mjs from this site. CMaps, standard font metrics, ICC profiles, and WASM helpers for pdf.js live under /pdfjs/ (copied from pdfjs-dist on npm install) so workers can fetch glyph data from the same origin.
  • That preview worker is separate from the merge/split/organize worker; both use Web Workers and stay entirely on your device.

Network & storage

  • Over the wire you should see requests for the app shell, JS chunks, CSS, fonts (next/font self-hosted subsets), icons, the PDF preview worker script, and (after npm install) same-origin OCR assets under /tesseract/—not outbound uploads of your document to SafePaper for processing.
  • Downloads use normal browser mechanisms (Blob / URL.createObjectURL) initiated by you.
  • We do not persist your PDFs to SafePaper storage; lifetime is in-memory for that tab session (and the shared client state resets when you leave the tool area for the home page).

Tool-by-tool: where work runs

Tool / areaWhere work runsExtra network
Merge, split, organize, protectBrowser + workersApp shell only
Compress, redact, cleanBrowser + workersApp shell only
Export (PNG / JPEG / text)Browser (pdf.js canvas)App shell only
Forms, watermark, page #, insertBrowser (pdf-lib)App shell only
OCRBrowser (pdf.js + Tesseract)Same-origin WASM/worker/lang after postinstall (no third-party OCR CDN)
Duplicate scan (Organize)Browser worker (pdf.js)App shell only
Share Desk (P2P)Browser WebRTC + OPFS workerSignaling WebSocket + STUN (optional TURN) — no file bytes to SafePaper
Media StudioBrowser + FFmpeg WASM (lazy) + image workersSame-origin FFmpeg under /vendor/ffmpeg/
Data ZoneWeb Workers + DuckDB-wasm + OPFS queuesDuckDB bundles may fetch from jsDelivr on first SQL use — not your table rows
Security VaultBrowser Web Crypto + jose (no upload)Analytics disabled on these routes
AI Desk (RAG)Embedding + chat workers; IndexedDB indexOne-time model weight downloads (Transformers.js / WebLLM CDN)
Record DeskCapture + OPFS mux; Whisper workerWhisper ONNX/WASM may fetch from jsDelivr on first caption run
Vision StudioImage inference worker (ONNX / Transformers.js)One-time model weight downloads (Hugging Face / jsDelivr); images stay local
Audio LabFFmpeg WASM worker + Web Audio; Whisper for transcriptionOne-time FFmpeg/Whisper asset downloads; audio samples stay local
Health Deskdicom-parser + canvas; pure-JS HL7/FHIR; localStorage lab historyNone — scans, records, and lab data are parsed and stored entirely on-device
Archive Deskzip.js + fflate in archive workerApp shell only (central directory parsed locally)
Data Roomcrypto-packager worker + offline HTML exportSame-origin /dataroom-template.html at build time

“App shell only” means HTML/JS/CSS/fonts and static assets from your host—no SafePaper API that accepts PDF bodies. A production service worker precaches the home page, PDF preview worker, and vendored OCR files for calmer offline reloads after the first visit.

Offline & limits

  • After the app has loaded once, cached bundles mean the core tools can keep working offline for files already held in memory—subject to browser cache eviction.
  • Practical limits are those of the device: available RAM, CPU, and browser tab limits. Malicious PDFs are still a local execution concern the same way opening a file in any desktop viewer is; we do not add a separate server-side malware scan because files never leave your machine for our processing.

Design rule

Zero server uploads for PDF work. New tools are expected to follow the same model: browser-first, worker offload where needed, and no silent exfiltration of document bytes to SafePaper infrastructure.

Privacy status

See what this page loaded. Your files stay on your device.

Live privacy status

Your audio stays on your device. FFmpeg and Whisper run locally. This panel shows what your browser loaded on this page.

Your audio sent to SafePaper0bytes · by design
Tab requests shown
0
Bundles, CSS, fonts…
0
fetch / XHR rows
0
Downloaded (assets)
—

How to read this: Audio work happens on your device. Requests below are usually app files and one-time engine/model downloads, not your recordings.

Network rowsTap for full list

No network rows yet. Reload once and they should appear after the page finishes loading.

Analytics preferences

You have not chosen yet — use the bar at the bottom of the screen, or choose below.

Optional analytics uses Vercel Web Analytics and Speed Insights for aggregated page and performance data only. We do not attach your PDFs or their contents to these tools.

Read the Privacy Policy section