FAQ

High-frequency questions and answers for FlowPick usage, covering installation, download, format conversion, and troubleshooting scenarios.

This document collects the most frequently asked questions during FlowPick usage. If your issue isn't listed here, please refer to Common Issues Troubleshooting or provide feedback via GitHub Issues.

Quick Navigation

Category	Question Count	Jump To
Installation & Setup	4	Installation & Setup
Media Detection	3	Media Detection
Download-Related	5	Download-Related
Format Conversion	3	Format Conversion
Privacy & Security	3	Privacy & Security
Technical Questions	3	Technical Questions
Other Questions	4	Other Questions

Installation & Setup

Is FlowPick free?

Yes, FlowPick is completely free with no paid features or subscription plans. The project code is open source on GitHub.

For open-source license and contribution methods, see Contributing Guide.

Why does the extension need "Read and change website data" permission?

FlowPick needs to monitor network requests to detect media resources on pages. This permission is only used for:

Monitoring network requests from browser to identify video, audio, and image URLs
Initiating download requests when user actively clicks download

FlowPick doesn't collect, upload, or share your browsing data.

For all permissions requested by extension and their specific purposes, see Privacy & Security — Permission Explanation. For extension installation steps, see Installation Guide.

Firefox extension version is under development. Currently you can use online tools on Firefox (/m3u8-downloader, /dash-downloader), but functionality limited by Firefox's support for File System Access API and SharedArrayBuffer.

For complete feature support matrix across browsers, see Browser Compatibility — Feature Support Matrix. For online tool usage, see Online Tools.

How do I update to latest version?

Chrome/Edge extensions auto-update. You can also manually check for updates:

Open chrome://extensions (Edge: edge://extensions)
Enable "Developer mode" in top-right corner
Click "Update" button

Extension Update Page

Media Detection

Why can't video on page be detected?

Most common causes and solutions:

Page hasn't loaded media yet: Play video for a few seconds first, then refresh page and reopen FlowPick
Extension activated after page loaded: Refresh page so extension re-monitors network requests
Website uses MSE dynamic loading: Some websites push data dynamically via Media Source Extensions; may not be detectable through regular network request monitoring
Media in iframe: Media in cross-origin iframes may not be detectable

For complete media detection troubleshooting flow (including diagnostic steps and common cause table), see Common Issues Troubleshooting — Media Detection Issues. For HLS/DASH detection technical principles, see Video Sniffing.

Too many files detected, how to filter?

Use filtering features in FlowPick popup:

Type filter: Switch between Video/Audio/Image tabs
Size filter: Set minimum file size to exclude thumbnails and small icons
Format filter: Filter by file extension (e.g., show only .mp4)

Media Filtering Interface

For detailed filter configuration documentation, see Configuration Reference — Filter Settings. For image download filtering tips, see Image Download.

Why does same video appear multiple times?

Streaming typically contains multiple quality versions (e.g., 720p, 1080p, 4K); each version displays as separate entry. Select desired quality to download. If using M3U8 stream with Master Playlist, FlowPick shows quality list for selection.

For distinction between Master Playlist and Media Playlist, see Video Sniffing — HLS Streams. For quality selection practical scenarios, see Online Course Download.

What to do about slow download speed?

Factors affecting download speed and optimization suggestions:

Factor	Optimization Method
Concurrent thread count too low	Increase to 4-6 in settings
CDN throttling	Reduce concurrency to avoid triggering rate limiting
Insufficient network bandwidth	Close other bandwidth-consuming apps
Segment server far away	Cannot optimize; depends on streaming service provider

For complete slow download diagnostic flow (including decision tree), see Common Issues Troubleshooting — Slow Download Speed. For relationship between concurrency and performance analysis, see Download Engine Architecture — Concurrency vs Performance.

Downloaded file won't play?

Troubleshoot with these steps:

Check file size: If file significantly smaller than expected (e.g., only few KB), download incomplete
Check format: Confirm player supports format (TS format requires VLC or PotPlayer)
Check encryption: If encrypted stream key fetch fails, file cannot be decrypted
Try remuxing: Convert TS to MP4 before playing

For complete file unplayable diagnosis steps (including VLC repair feature), see Common Issues Troubleshooting — File Won't Play After Download. For TS and MP4 format player compatibility, see Format Conversion — Output Format Selection.

Can I download multiple files simultaneously?

Yes. Check multiple resources in popup and click "Download Selected"; they will download sequentially one by one.

For batch download queue management, concurrency control, and status management, see Batch Download. For batch image download scenarios, see Image Gallery Batch Download.

Can I resume interrupted downloads?

Current version doesn't support resumable downloads. If download interrupted:

Already downloaded segment data will be lost
Need to restart download from beginning
Recommend using stable network environment for large file downloads

Why No Resumable Downloads?

Resumable downloads require persisting downloaded segment data to disk and continuing from breakpoint on recovery. This faces two main challenges in browser environment:

Storage limitations: Browser storage (IndexedDB) has quota limits; cannot reliably store GB-level segment data
Segment URL expiration: Streaming segment URLs usually contain time-sensitive tokens; even short interruption causes token expiration, preventing remaining segments from downloading even if resumed

For typical time windows of segment URL expiration, see Known Limitations — Segment URL Expiration. For download engine retry mechanism, see Download Engine Architecture — Retry Mechanism.

Where are downloaded files saved?

Depends on browser settings and selected save method:

Chrome default: Browser's default download directory (usually "Downloads" folder)
Select directory mode: Folder specified through directory picker
Ask every time: Save dialog pops up each time you download

For File System Access API directory selection functionality and permission persistence, see Download Engine Architecture — File Write Module. For save method support across browsers, see Browser Compatibility — Feature Support Matrix.

Format Conversion

What's the difference between TS and MP4?

Feature	TS	MP4
Full Name	MPEG Transport Stream	MPEG-4 Part 14
Designed For	Streaming transmission	Local storage and playback
Playback Compatibility	Requires professional players like VLC/PotPlayer	Almost all players supported
File Size	Slightly larger (includes transport overhead)	Slightly smaller
Download Speed	Fast (no remuxing needed)	Slow (requires FFmpeg processing)

Recommendation: If player supports TS format, selecting TS output skips remuxing step for faster downloads.

For distinction between containers and codecs, see Format Conversion — Containers & Codecs. For distinction between remuxing and transcoding, see Known Limitations — Unsupported Conversions.

Why does remuxing take a long time?

FFmpeg runs as WebAssembly in browser; performance approximately 10-20% of native version. Influencing factors:

File size: Larger files remux slower
SharedArrayBuffer: Only single-thread operation when unavailable
CPU performance: WASM execution speed depends on device CPU

For performance comparison data between FFmpeg WASM and native version, see Known Limitations — FFmpeg WASM Performance. For SharedArrayBuffer configuration requirements, see Browser Compatibility — Advanced APIs.

What to do when remuxing fails?

Common causes and solutions:

FFmpeg load failure: Refresh page and retry, check network connection
Insufficient memory: Close other tabs, reduce concurrency
Source file corrupted: Some segments downloaded incompletely, try re-downloading
Unsupported codec: FlowPick only does container conversion; unsupported codec formats cannot be processed

For FFmpeg WASM loading flow and first-load time breakdown, see Known Limitations — Slow First FFmpeg Load. For merge process stuck troubleshooting, see Common Issues Troubleshooting — Merge Process Stuck.

Privacy & Security

Does FlowPick collect my data?

No. All processing by FlowPick completes locally in your browser:

Media detection happens inside extension; no data uploaded
File downloads directly from source server to your disk
No backend servers, no user account system
Google Analytics used only for anonymous visit statistics (can be blocked by ad blockers)

For complete privacy protection documentation (including permission purposes, data processing flow, security architecture), see Privacy & Security. For full privacy policy text, see Privacy Policy.

Are there copyright issues with downloaded content?

FlowPick is a tool that neither judges nor restricts what you download. Please follow these principles:

Only download content you have right to access and use
Comply with website terms of service
Use downloaded content for personal fair use only
Don't use downloaded content for commercial purposes or redistribution

Are online tools safe?

All processing for online tools (/m3u8-downloader, /dash-downloader) also completes locally in browser:

Pasted URLs aren't sent to any server
Downloaded data transfers directly from source server to your disk
FFmpeg runs in browser; files not uploaded

For functional differences and security model between online tools and extension, see Online Tools.

Technical Questions

What is SharedArrayBuffer, why is it needed?

SharedArrayBuffer is a JavaScript object allowing multiple threads to share memory. FFmpeg WASM uses it to implement multithreaded parallel processing, significantly improving remuxing speed.

For security reasons (Spectre vulnerability mitigation), browsers require website to set specific HTTP response headers to use SharedArrayBuffer. If headers aren't set, FFmpeg automatically degrades to single-thread mode.

For SharedArrayBuffer browser support details and server-side configuration during self-deployment, see Browser Compatibility — Advanced APIs. For single-thread vs multi-thread performance difference, see Format Conversion — Multithreading Mode.

Why do online tools require pasting URL instead of auto-detecting?

Browser extensions can monitor network requests, but ordinary web pages restricted by same-origin policy cannot access other tabs' network request data. Online tools run as ordinary web pages, requiring you to manually provide streaming URL.

How to Get Streaming URL?

Press F12 to open Developer Tools
Switch to Network panel
Type m3u8 or mpd in filter box
Play video, observe appearing requests
Right-click M3U8/MPD request → Copy → Copy link address

Developer Tools Getting M3U8 URL

For complete online tool usage flow, see Online Tools. For CORS cross-origin restriction technical principles, see Known Limitations — CORS Cross-Origin Restrictions.

What's the difference between extension version and online tools?

Feature	Extension Version	Online Tools
Auto-detect media	Supported	Not Supported
CORS restrictions	Not restricted	Restricted
Installation required	Need install extension	No installation needed
Ease of use	One-click detect & download	Manually obtain URL needed
Use case	Daily usage	Temporary use, environments where extension can't be installed

For detailed functional differences and selection recommendations between extension and online tools, see Online Tools — Comparison with Extension. For extension installation steps, see Installation Guide.

FAQ