DEV Community: siwet zhou

How I Recorded 10 Hours of My Screen in 3 MB Using WebCodecs

siwet zhou — Fri, 17 Apr 2026 09:17:39 +0000

Last week I needed to debug an AI agent that runs for ~8 hours overnight. I wanted to see what it did — but not as 30+ GB of continuous video. So I built a browser-based timelapse screen recorder. 10 hours of screen activity now fits in a few MBs.

The project is live at s.sum.pub (cloud + sharing) and re.sum.pub (recorder). This post is about how the recorder part works.

The problem with normal screen recording

Continuous 1080p @ 30fps is ~5-10 MB per minute with a good codec. An 8-hour session is 2-5 GB. For workflows where you review rather than watch — training runs, agent runs, quant backtests, overnight debugging — that's a huge amount of data for footage you'll scrub through at 10x.

But scrubbing is most of what you do. What you actually need is one frame every few seconds.

The core idea: frame-interval capture via WebCodecs

Instead of recording 30fps continuously, capture one frame every N seconds and encode just those frames into an MP4. 10 hours at 1 frame / 5s = 7,200 frames. At ~0.5 KB per encoded frame (H.264, heavily delta-compressed), that's ~3.5 MB.

The whole pipeline is browser-native:

getDisplayMedia() — prompt the user to share a screen/window/tab
Read a frame from that stream every N seconds
Feed frames to VideoEncoder (WebCodecs)
Mux encoded frames into MP4 with mp4-muxer
Save as a blob / upload to cloud

No FFmpeg. No WASM builds. No native app. Everything is 2024+ browser API.

Sketch of the capture loop

const stream = await navigator.mediaDevices.getDisplayMedia({ video: true });
const track = stream.getVideoTracks()[0];
const processor = new MediaStreamTrackProcessor({ track });
const reader = processor.readable.getReader();

const encoder = new VideoEncoder({
  output: (chunk, meta) => muxer.addVideoChunk(chunk, meta),
  error: (e) => console.error(e),
});

encoder.configure({
  codec: 'avc1.42E01F',       // H.264 baseline
  width: 1920, height: 1080,
  bitrate: 500_000,           // low — we're only encoding a few frames/sec
  framerate: 20,              // playback fps, not capture fps
});

let frameIndex = 0;
const INTERVAL_MS = 5000;      // one frame every 5 seconds

while (recording) {
  const { value: frame } = await reader.read();
  if (!frame) break;

  encoder.encode(frame, { keyFrame: frameIndex % 60 === 0 });
  frame.close();
  frameIndex++;

  await sleep(INTERVAL_MS);
}

await encoder.flush();
const mp4Blob = muxer.finalize();

A few subtle things worth calling out:

1. Capture fps ≠ playback fps

The encoder is configured at 20 fps. The capture loop sleeps 5 seconds between frames. The result is a perfectly valid MP4 where each "frame" represents 5 real-world seconds. Played at 20fps, 10 real hours play back in 6 minutes. Scrub-friendly.

2. Keyframe every N seconds, not every N frames

For scrubbing performance, you want keyframes close together. But every frame is already ~a single keyframe-worth of change (5 seconds apart). Forcing a keyframe every ~60 seconds of "wall clock" keeps seek-times fast without blowing up file size.

3. Frames must be closed

VideoFrame objects are backed by native memory. If you don't .close() them after .encode() returns, you will OOM the tab in about 10 minutes. Ask me how I know.

4. `MediaStreamTrackProcessor` is Chromium-only (for now)

Firefox and Safari don't ship MediaStreamTrackProcessor yet. On those you fall back to drawing the stream to a <canvas> and new VideoFrame(canvas). Slower, but works.

What this enables

Because files are small, the companion cloud (s.sum.pub) just stores them as regular objects and hands out share URLs. No transcoding pipeline, no CDN drama. Upload a 3 MB timelapse, share a link, done.

Concrete use cases I've heard from early users:

AI agent debugging — let Claude / Cursor / your agent run for 4 hours, review as a 2-minute timelapse
Quant backtests — record the run, share with the team
Long tutorials — a 3-hour course becomes a scrubbable index
Overnight builds/monitors — catch "when exactly did this break?" without SIEM

Try it

Recorder: re.sum.pub — pick an interval (1-60s), hit record
Cloud: s.sum.pub — upload, share public or private

Feedback very welcome — especially from anyone who's pushed WebCodecs further or has war stories about the same trade-offs.

How to Transfer Files from Phone to PC Without a Cable (2025 Guide)

siwet zhou — Fri, 10 Apr 2026 03:34:19 +0000

Still using a USB cable to move photos from your phone to your computer? There are much better ways now.

In this guide, I'll show you 5 methods to transfer files wirelessly between your phone and PC — from the quickest no-setup option to more advanced solutions.

Method 1: Use a Browser-Based Transfer Tool (Fastest)

The quickest method requires zero installation. Tools like Quick Transfer (t.sum.pub) let you send files between devices using just your web browser.

How it works:

Open t.sum.pub on your phone
Open t.sum.pub on your computer
Select a file and send

That's it. Files transfer directly over your local Wi-Fi network, so they never leave your home. Works with any phone (iPhone, Android) and any computer (Windows, Mac, Linux).

Best for: Quick one-off transfers when you don't want to install anything.

Method 2: Cloud Storage (Google Drive, iCloud, OneDrive)

Upload to the cloud from your phone, download on your computer. Simple, but:

Requires an account
Uses internet bandwidth (slow for large files)
Files are stored on someone else's server
Free storage is limited (15GB for Google, 5GB for iCloud)

Best for: Files you also want backed up to the cloud.

Method 3: Email / Messaging Apps

The classic "email it to yourself" approach. Or send via WhatsApp/Telegram/Slack.

Attachment size limits (usually 25MB for email)
Compresses images and videos
Clutters your inbox

Best for: Small files when you're in a hurry and don't mind compression.

Method 4: AirDrop / Quick Share

Apple's AirDrop and Google's Quick Share are built-in solutions. They work well within their ecosystems but fail at cross-platform transfers.

AirDrop: iPhone/Mac only
Quick Share: Android/Windows only
Neither supports iPhone to Windows or Android to Mac

Best for: Transfers within the same ecosystem.

Method 5: Dedicated Apps (LocalSend, SHAREit)

Apps like LocalSend and SHAREit need to be installed on both devices.

Requires installation on both devices
SHAREit has ads and privacy concerns
LocalSend is open source but less polished

Best for: Frequent transfers when you don't mind installing an app.

My Recommendation

For most people, a browser-based tool like Quick Transfer is the best balance of speed, privacy, and convenience. No app to install, no account to create, and your files stay on your local network.

Try it at t.sum.pub — it takes about 3 seconds to start transferring.

Why I Stopped Using Cloud Storage to Transfer Files Between My Devices

siwet zhou — Mon, 16 Mar 2026 10:02:15 +0000

I used to email files to myself. Then I graduated to Google Drive. Then AirDrop. Each "upgrade" still felt like a hack.

Here's the thing: I just want to move a file 3 feet — from my phone to my laptop. Why does that require:

An internet connection (cloud storage)
A specific ecosystem (AirDrop)
Installing an app (SHAREit, LocalSend)
A USB cable (it's 2025)

The Problem Nobody Talks About

Every major file transfer solution assumes you want to do more than just transfer a file. Cloud storage wants to sync and back up. AirDrop wants you to buy all Apple. SHAREit wants to show you ads. Even Bluetooth wants you to spend 10 minutes pairing.

But 90% of the time, I literally just want to move a photo or document from my phone to my computer. That's it.

The Browser Already Solves This

Modern browsers can do WebRTC peer-to-peer connections. They can handle file I/O. They run on every device. So why are we still installing apps?

I found Quick Transfer (t.sum.pub) which takes exactly this approach:

Open the website on both devices
Transfer files directly between them
Done

No app. No account. No cloud. Files go directly from phone to computer over your local Wi-Fi.

What I Like About This Approach

Privacy by default. Files never leave your network. There's no server to hack, no data to leak, no privacy policy to read.

Zero friction. There's nothing to install, nothing to sign up for, and nothing to configure. If you can open a website, you can transfer files.

Truly cross-platform. It works on literally everything — iPhone, Android, Windows, Mac, Linux, ChromeOS. If it has a browser, it works.

What I Miss About Apps

Fair is fair — dedicated apps do have advantages:

Offline discovery: Apps like LocalSend can find devices without internet. Browser tools need your local network.
Background transfers: Apps can transfer in the background. Browsers need to stay open.
Integration: AirDrop's deep OS integration is genuinely nice (when it works, and when you're all-Apple).

My Setup Now

For quick transfers (photos, documents, random files): Quick Transfer (t.sum.pub). Open, send, close. Takes 10 seconds.

For large syncs (project folders, backups): Cloud storage (Syncthing for private, Google Drive for shared).

For Apple-to-Apple: AirDrop still works fine.

The key insight is that different tools for different jobs beats one tool that tries to do everything poorly.

What's your file transfer setup? Am I the only one who overthinks this? Let me know in the comments.

10 Best Free Tools to Transfer Files Between Phone and PC (2025)

siwet zhou — Mon, 16 Mar 2026 06:55:35 +0000

Transferring files between your phone and computer shouldn't require cables, cloud accounts, or installing apps. Yet most people still email files to themselves or plug in a USB cable.

Here are the 10 best free tools for transferring files between your phone and PC — ranked by ease of use, speed, and privacy.

1. Quick Transfer (t.sum.pub)

Best for: Instant browser-based transfers with zero setup

Quick Transfer is the simplest file transfer tool I've found. Open t.sum.pub on both your phone and computer, and you can send files instantly. No app to install, no account to create, no cloud storage involved.

Files transfer directly between your devices over the local network, which means your data never touches a third-party server. It works on iOS, Android, Windows, Mac, and Linux — anything with a browser.

Pros:

Zero setup — works in any browser
No account or app required
Files stay on your local network (private)
Supports text and files
Works across all platforms

Cons:

Both devices need to be on the same network
No cloud backup option

2. AirDrop (Apple)

Best for: Apple-to-Apple transfers

AirDrop is built into every iPhone, iPad, and Mac. It's fast and seamless — when it works. The biggest limitation is that it only works within the Apple ecosystem. If you have an Android phone or Windows PC, AirDrop won't help you.

Pros:

Built into Apple devices
Very fast transfers
No internet required

Cons:

Apple-only — no Android or Windows support
Can be unreliable with discovery
Requires Bluetooth and Wi-Fi enabled

3. Nearby Share / Quick Share (Google)

Best for: Android-to-Android or Android-to-Windows

Google's answer to AirDrop. Works between Android devices and now has a Windows app. Still doesn't support Mac or iOS natively.

Pros:

Built into Android
Windows app available
No internet required

Cons:

No Mac or iOS support
Requires Google account on some setups
Windows app needs installation

4. Snapdrop

Best for: Open-source browser-based transfers

Snapdrop is an open-source alternative that works similarly to Quick Transfer. It's browser-based and uses WebRTC for peer-to-peer transfers. However, it can be less reliable on some networks.

Pros:

Open source
Browser-based
No account needed

Cons:

Can fail on certain network configurations
No text transfer
Original project is sometimes offline

5. Send Anywhere

Best for: Transfers across different networks

Send Anywhere generates a 6-digit key that you enter on the receiving device. This means it works across different Wi-Fi networks, but files do pass through their servers.

Pros:

Works across different networks
Available on all platforms
Simple key-based sharing

Cons:

Files go through their servers
App installation recommended
Has ads in the free version

6. SHAREit

Best for: Large file transfers on mobile

SHAREit was once the go-to file sharing app, especially in Asia. It creates a direct Wi-Fi connection between devices. However, it's become bloated with ads and has had security concerns.

Pros:

Very fast transfers
Works without internet

Cons:

Heavy ads and bloatware
Privacy and security concerns reported
Large app size

7. LocalSend

Best for: Privacy-focused users who don't mind installing an app

LocalSend is an open-source app that works on all platforms. It's privacy-focused and keeps everything on your local network. The downside is you need to install the app on each device.

Pros:

Open source
Cross-platform
Privacy-focused

Cons:

Requires app installation
UI is less polished
Can be slow to discover devices

8. Tresorit Send

Best for: Encrypted file sharing with links

Tresorit Send lets you create encrypted links to share files. It's more of a file-sharing service than a direct transfer tool, but it's good for sharing sensitive documents.

Pros:

End-to-end encryption
No account needed to send
Link-based sharing

Cons:

5GB limit on free plan
Files go through cloud servers
Not real-time transfer

9. KDE Connect

Best for: Linux and Android power users

KDE Connect integrates your Android phone with your Linux desktop. It does much more than file transfer — clipboard sharing, notification mirroring, remote control. But it requires setup and is mainly for Linux users.

Pros:

Deep system integration
Many features beyond file transfer
Open source

Cons:

Mainly Linux + Android
Requires installation and setup
Learning curve

10. WeTransfer

Best for: Sending large files to anyone via link

WeTransfer is a well-known file sharing service. Upload your file, get a link, share it. Simple, but files go through their cloud and there are size limits on the free plan.

Pros:

Very well known
Simple interface
No account needed for basic use

Cons:

2GB limit on free plan
Files go through cloud
Not instant — upload then download
Files expire after 7 days

Quick Comparison Table

Tool	No Install	No Account	Cross-Platform	Private (Local)	Free
Quick Transfer	✅	✅	✅	✅	✅
AirDrop	✅	✅	❌ Apple only	✅	✅
Quick Share	❌	❌	❌ Limited	✅	✅
Snapdrop	✅	✅	✅	✅	✅
Send Anywhere	❌	❌	✅	❌	✅
SHAREit	❌	❌	✅	✅	✅*
LocalSend	❌	✅	✅	✅	✅
Tresorit Send	✅	✅	✅	❌	✅*
KDE Connect	❌	✅	❌ Limited	✅	✅
WeTransfer	✅	✅	✅	❌	✅*

* Has paid tiers or ads

The Bottom Line

If you want the fastest, zero-friction way to move files between your phone and computer, Quick Transfer (t.sum.pub) is hard to beat. No installation, no accounts, no cloud — just open the website on both devices and transfer. For Apple-only households, AirDrop remains excellent. And if you need to send files across different networks, Send Anywhere or WeTransfer are solid choices.

I Built a Browser-Based File Transfer Tool Between Phone and PC

siwet zhou — Fri, 13 Mar 2026 07:43:11 +0000

The Problem

Every developer knows this pain: you need to get a file from your phone to your computer.

Email it to yourself (works, but feels ridiculous)
Upload to Google Drive (requires login, slow for one file)
AirDrop (only works in Apple's ecosystem)
USB cable (who carries those anymore?)

The Solution

I built Quick Transfer - a web tool that sends files between any two devices using just a browser.

How it works:

Open t.sum.pub on both devices
Select a file
It transfers directly

No app to install. No account to create. No cloud storage.

Why I Built This

I work across multiple devices daily. Moving files between them was always annoying. I wanted something that:

Works on any device with a browser
Requires zero setup
Is fast - direct transfer
Is free

Try It Out

Try it now: t.sum.pub

Open it on your phone and computer, transfer a file. Would love your feedback!

What's Next

Folder transfer support
Transfer history
QR code pairing

Let me know what you think in the comments!

I Built a Screen Recorder That Captures 1 Frame Every 10 Seconds (For AI Coding Sessions)

siwet zhou — Fri, 06 Feb 2026 11:20:04 +0000

The Problem

If you're using AI coding assistants like Claude Code, Cursor, or GitHub Copilot, you've probably wanted to record your sessions for later review.

But here's the issue: normal screen recorders capture at 30-60 fps. An 8-hour coding session becomes a 50GB+ file, and your CPU is working overtime the whole time.

The Insight

For reviewing a coding session, you don't need 60 frames per second. You need to see what changed over time. 1 frame every 10 seconds is more than enough.

The Solution

I built Slow Recording – a browser-based screen recorder that:

Captures 1 frame every N seconds (configurable 1-60s)
Produces tiny files (10 hours ≈ few MBs)
Has zero performance impact
Requires no installation

How It Works

The app uses the WebCodecs API to:

Capture screen frames at the specified interval
Encode them into a standard video format
Let you download and scrub through your session

Use Cases

AI pair-programming review: See which prompts worked, which didn't
Long workflow documentation: Record a whole workday
Background recording: Set it and forget it

Try It

It's free and open in your browser: re.sum.pub

Would love feedback from fellow developers! Especially interested in:

Other use cases I haven't thought of
Feature requests
Technical suggestions

Built with vanilla JS and the WebCodecs API. Happy to answer questions about the implementation!

DEV Community: siwet zhou

How I Recorded 10 Hours of My Screen in 3 MB Using WebCodecs

The problem with normal screen recording

The core idea: frame-interval capture via WebCodecs

Sketch of the capture loop

1. Capture fps ≠ playback fps

2. Keyframe every N seconds, not every N frames

3. Frames must be closed

4. MediaStreamTrackProcessor is Chromium-only (for now)

What this enables

Try it

How to Transfer Files from Phone to PC Without a Cable (2025 Guide)

Method 1: Use a Browser-Based Transfer Tool (Fastest)

Method 2: Cloud Storage (Google Drive, iCloud, OneDrive)

Method 3: Email / Messaging Apps

Method 4: AirDrop / Quick Share

Method 5: Dedicated Apps (LocalSend, SHAREit)

My Recommendation

Why I Stopped Using Cloud Storage to Transfer Files Between My Devices

The Problem Nobody Talks About

The Browser Already Solves This

What I Like About This Approach

What I Miss About Apps

My Setup Now

10 Best Free Tools to Transfer Files Between Phone and PC (2025)

1. Quick Transfer (t.sum.pub)

2. AirDrop (Apple)

3. Nearby Share / Quick Share (Google)

4. Snapdrop

5. Send Anywhere

6. SHAREit

7. LocalSend

8. Tresorit Send

9. KDE Connect

10. WeTransfer

Quick Comparison Table

The Bottom Line

I Built a Browser-Based File Transfer Tool Between Phone and PC

The Problem

The Solution

Why I Built This

Try It Out

What's Next

I Built a Screen Recorder That Captures 1 Frame Every 10 Seconds (For AI Coding Sessions)

The Problem

The Insight

The Solution

How It Works

Use Cases

Try It

4. `MediaStreamTrackProcessor` is Chromium-only (for now)