Download like
someone who knows what they're doing

Step by step:

1. Open Download SIU and paste the URL of the video, or of the page it's playing on.

2. Switch to PRO mode to expose the advanced options.

3. Pick your resolution — 4K, 2K, 1080p, whatever the source actually has.

4. Set FPS to Original so the frame rate matches the source exactly.

5. Choose MKV as the container to preserve everything.

6. Hit download and let the queue do the rest.

Pro tip: always use MKV for 4K. It carries higher bitrates and multiple audio tracks without forcing a re-encode, which is where quality quietly disappears.

FLAC — lossless compression, bit-for-bit identical to the source. Roughly 30 MB per track. Use it for archives and anything you might re-encode later.

MP3 320 kbps — high quality, plays literally everywhere. About 8 MB per track. The safe default for day-to-day listening.

MP3 128 kbps — noticeably compressed but tiny, around 3 MB per track. Fine for spoken word, podcasts or a phone that's nearly full.

How to extract: switch to the AUDIO EXTRACT tab, choose format and bitrate, paste the URL and download.

Method 1 — playlist URL. Paste the full playlist address and SIU detects every video in it automatically.

Method 2 — the queue. Add as many individual URLs as you like; they're processed in order without you touching anything.

Method 3 — full season. For series, enable season download and SIU walks from episode to episode on its own.

Getting the most out of it: raise the CPU-thread slider in PRO mode, download to an SSD rather than a mechanical drive, and keep the connection stable — interrupted segments are what actually slows a batch down.

Facebook Reels, logged out: paste a profile's Reels tab while you're not logged into Facebook in your browser, and Facebook itself only reveals around 10 reels before it demands a login — that's a limit on their end, not something SIU controls. Workaround until native login support lands: open the specific reel you want and paste its own URL instead of the profile link; SIU downloads those one by one with no limit at all.

MKV (Matroska)

Carries multiple audio tracks and multiple subtitle tracks in one file, tolerates higher bitrates, and rarely forces a re-encode. Right choice for films, series and anything you're keeping.

MP4 (MPEG-4)

Plays on essentially every device and platform ever made, and the files come out smaller. Right choice for phones, social uploads and sending things to other people.

Rule of thumb: archive in MKV, share in MP4.

30 FPS — the standard for film and television. Smooth enough for almost everything that isn't fast motion.

60 FPS — gaming footage, sports, anything with quick camera movement. The jump from 30 is genuinely visible.

120 FPS — professional gaming capture and usable slow motion. Demands real hardware to play back properly.

240 FPS — extreme slow motion and sports analysis. The files are enormous; only reach for it if you're going to slow the footage down.

Setting it: in PRO mode, choose the FPS from the dropdown. Leave it on Original unless you have a reason not to — forcing a different rate triggers a re-encode.

128 kbps — fine on a phone with earbuds on a noisy commute. ~3 MB per track.

256 kbps — high quality, and the point past which most people genuinely can't hear a difference. ~6 MB per track.

320 kbps — the ceiling for MP3. ~8 MB per track.

Quick reference:

• Phone with earbuds → 128–256 kbps
• Car audio → 256 kbps
• Home stereo → 320 kbps
• Archive or mastering → FLAC, lossless

In PRO mode the AUDIO and SUBS selectors let you decide exactly which streams survive the download.

AUDIO → All keeps every language the source publishes. Main keeps only the primary track and produces a much smaller file.

SUBS → All embeds every subtitle track as a selectable stream. None discards them entirely.

Important: multiple audio and subtitle tracks require the MKV container. MP4 will silently drop most of them.

Use ECO when you're happy with whatever quality the source has. There's no re-encode, so the download finishes in a fraction of the time and your CPU stays idle. The file is identical to the original, just rewrapped.

Use PRO when you need a specific resolution or frame rate, want to drop audio tracks or subtitles, or are targeting a device with strict format requirements. That means re-encoding, which is slower and works your CPU hard.

Rule of thumb: start in ECO. Move to PRO only when the file it produced isn't what you needed.

What it means: if your source file's codec already matches what you're converting to, and only the container needs to change (say, MKV to MP4), Convert copies the audio/video streams as-is instead of decoding and re-encoding them.

Why it matters: a job that would normally take several minutes finishes in a few seconds, with zero quality loss — nothing is re-compressed.

You don't choose it: Convert checks automatically, per file. There's no toggle to remember or forget.

When it can't apply: the moment an actual codec, resolution or bitrate change is needed, Convert falls back to a normal encode on its own.

Works for audio too: the same instant-copy logic applies to audio-only conversions, not just video.

What it does: a free local AI engine listens to the audio and separates it into two layers — the voice and everything else (music, instruments, effects).

Three ways to use it: keep only the vocals, keep only the instrumental, or export both as separate files.

Karaoke mode: inside Subtitle + AI, the instrumental becomes an extra selectable audio track next to the original, so you can follow the burned-in lyrics while the vocals are gone.

Recombine freely: mix voice, music and video back together afterward in any order you want.

Same engine, no extra cost: it's the free local engine used across the app — no API key needed, though you can optionally connect your own cloud provider for extra speed.

Pick a target: use the one-tap preset for Discord, WhatsApp or an email attachment, or type your own size in MB.

How it works: Convert calculates the bitrate needed to land just under that size from the file's real length, then encodes it in a single pass.

No guessing: no re-exporting three times to see if it fits — it's figured out before the encode starts.

Quality stays as high as the size allows: it uses every bit of the budget you gave it, not less.

Small safety margin: the result lands slightly under the limit on purpose, so it never gets rejected for being a few KB over.

What it's for: join the parts or episodes you just downloaded — or any set of clips — into one continuous file.

Order is yours: arrange them top to bottom in the list before exporting; that's the order they play in.

One clean output: a single file comes out the other end, ready to play or share — no separate editor needed.

Runs locally: like every other tool in the app, nothing is uploaded anywhere to do this.

Tip: make sure every clip shares the same resolution and frame rate first if you want a perfectly seamless join.

Local engine (default): transcribes speech in 99 auto-detected languages and translates into 75, entirely on your PC. No internet needed, no cost, no account.

When to switch to your own key: mainly for speed — the local engine runs on your hardware, while OpenAI/DeepL process on their servers.

OpenAI key: handles both transcription and translation. Needs a paid account with balance loaded.

DeepL key: translation only, very fast — useful if you already have a transcript and just need it in another language.

Your key stays yours: it's encrypted and saved only on your PC; Download SIU never sees or stores it, and the app automatically falls back to the next saved key if one runs out of balance.

Still being refined: subtitle AI is a work in progress. Transcription and translation do work, but accuracy depends on the audio quality, so review the result before relying on it. We are actively improving it, and this note will be updated once it is consistently reliable.

One export, not two steps: the vertical 9:16 crop and the burned-in subtitle happen in the same pass — no separate video editor.

Output: straight to 1080×1920, ready to upload as-is.

Face tracking (optional): a small on-demand AI pack keeps the speaker centered as they move, instead of a fixed crop in the middle of the frame.

Never blocks the export: if no face is found, it quietly falls back to a centered crop instead of failing.

Where to find it: it's an export option inside Subtitle + AI, right alongside the normal file/embed/burn-in choices.

Separates voices from music first, so the new dub sits over the original score and effects instead of erasing them.

Detects each speaker — who talks, and exactly when (diarization) — before translating a single line.

One fixed voice per speaker, picked from a real voice catalog to match male/female, and kept consistent for the whole video so characters don't swap voices between lines.

Does not clone the original actor's voice — reliable, free, offline voice-cloning isn't there yet. You get a clean, consistent catalog voice instead, which is what most re-dubs actually need.

9 output languages, with the best available voice engine chosen automatically for whichever one you pick.

Still being refined: changing a video's audio language is a work in progress. It already works from start to finish, but the result is not always natural — voices can sound flat, and timing or volume balance on long videos may need adjusting. We are actively improving it, and this note will be updated once it is consistently solid.

Fast Mode — static mark, flat background: instant one-click filters (reconstruct, blur, pixelate or crop). Seconds, light on the CPU.

Precise Mode — any shape, by hand: draw rectangles, circles, polygons or freehand over the mark; a pixel mask erases exactly what you outlined.

Exact Mode — see-through logos: measures how transparent the watermark is and recovers the real pixels underneath mathematically, instead of guessing. Minutes, not hours.

AI Mode — textures and fine detail: a local engine reconstructs what was actually behind the mark. Downloaded once, runs on your GPU or CPU, nothing uploaded.

Not sure? Compare first: the before/after slider lets you check the result of any engine before committing, on one video or the whole batch.

Auto-detect: samples 40 frames across the file and finds what stays still while the rest of the picture changes — gives you candidates with a confidence score, and the best one applies itself.

Motion tracking: for a watermark that bounces around the frame (common on short-form vertical video) — mark it once, press Track motion, and it follows frame by frame.

Add your own mark afterward: text or logo, with font, color, opacity, rotation, outline, shadow and nine anchor positions — on one video or the whole batch.

Save it as a recipe: mode, method, intensity and output format, optionally with the marked zones — apply it to the next video or the whole batch in one click.

Keeps what matters: subtitles, chapters, fonts and metadata carry over when the output container allows it, and the app tells you plainly when it can't.

Why Android blocks it: apps from the Play Store go through Google's automatic scanning before you ever see them. A file you download directly — from any developer's own website, not just this one — skips that scan, so Android shows a one-time warning and waits for your explicit OK before installing it. It's a standard Android safeguard, not a sign that something is wrong with the specific file.

The setting: "Install unknown apps", and it's per-app — it asks which app you used to open the downloaded file (usually your Files app, or your browser), not which app you're installing.

Where to find it: Settings → Apps → pick the app you opened the file with → "Install unknown apps" (on some phones it's under Settings → Security instead). Turn that one toggle on for that one app.

Shortcut: when Android shows the "can't install unknown apps" warning, there's usually a Settings button right on that same screen — it drops you straight into the exact toggle, no need to hunt for it by hand.

After that: tap Install again (or reopen the downloaded file) and it installs normally. You only need to allow it once per app you use to open files — updating again later won't ask twice.

The idea: SIU downloads directly from the source, the same way your browser does — so if a page needs you logged in to see something, SIU needs that same login info (your session cookies) to see it too. It never asks for your password; it only reuses the session your browser already has.

Step 1 — log in normally on the site, in your regular browser, the way you always do.

Step 2 — export your session. Install the free, open-source extension "Get cookies.txt LOCALLY" (search it by that exact name in your browser's extension store — there's an older, unrelated extension with a similar name that isn't this one). With the site's tab open, click the extension icon → Export (Netscape format) → save the file.

Step 3 — hand it to SIU. Rename the saved file to exactly cookies.txt and place it in %APPDATA%\Download-SIU\cookies.txt (paste that path straight into a File Explorer address bar). SIU checks that exact file automatically before every download — no setting to flip, no restart needed.

It expires on purpose: SIU only trusts that file for 24 hours after you last saved it — a sensible safety limit for something that can access your logged-in session. Past that, just repeat step 2 to refresh it. (YouTube and Facebook already have their own one-click "Connect" button inside the app — this method is for everything else.)

Why it survives: the real work runs in an Android foreground service, not inside the app window. Closing the window, or swiping the app away from Recents, doesn't kill it.

The notification is your status bar: "Downloading…" means it is genuinely working in the background. Tap it to reopen the app, but you don't have to for it to keep going.

Lost signal? It waits and picks up again on its own from where it stopped — nothing to restart by hand.

What does stop it: force-stopping the app from Android Settings → Apps, or switching the phone off.

Why it happens: Xiaomi, Samsung, Huawei, Oppo and a few others add extra battery rules on top of Android's own, and those can close apps that Android itself would have left running.

What the app already does: it asks Android to ignore battery optimization for it. If your phone still closes it, that's one of those extra brand layers — not a bug in the app.

What to do: in your phone's battery settings look for "Autostart", "App battery saver" or "No restrictions" (the name changes by brand) and allow it for Download SIU specifically.

Once is enough: that decision belongs to you, so the app can't set it on your behalf — but you only do it once per phone.

How: in the Library, every finished download has a small ✈️ button — tap it to send that exact file to your Download SIU on PC.

Same WiFi required: the file goes directly from phone to PC across your local network — it never travels over the internet or through any server.

PC side: Download SIU just needs to be open on your PC (it doesn't have to be the active window) to receive it.

When it's handy: big files you'd rather not stream over mobile data, or keeping a copy in your PC library without downloading it again.

The limit: the server only processes a sensible number of downloads per account at once, so one phone downloading a lot doesn't starve everyone else's queue.

What happens: when you're at that limit, the next download queues and starts by itself the moment a slot frees up — nothing for you to do.

When it doesn't apply: downloads the phone can fetch directly from the source don't go through that server step.

If it feels stuck for a long time: that points to a connection problem rather than the queue — check your signal.

How it works: if a file with that exact name already exists in your folder, the new one is saved as "Name (2).mp4", then "(3)" and so on — it never replaces what is already there.

Whatever the source: it applies whether the duplicate came from downloading the same link again or from a file you had already saved yourself.

Nothing at risk: a file you already have is never silently overwritten by a new download that happens to share its name.

Pause is not cancel: a paused conversion keeps everything it has already processed and continues from that point when you resume — it does not start over.

Cancel is the one that discards: use it only when you don't want that output at all. To free up your PC for a moment, pause.

Lowering the limit pauses too: if you reduce how many conversions may run at once while some are mid-way, the extra ones are paused rather than killed.

The simple switch: "Clean metadata" removes the tags the original uploader and the source put into the file.

The custom option: instead of leaving the tags empty, you can write your own values (such as an artist name and a comment) into every file, consistently, without touching each one by hand afterwards.

Finished file only: both options affect the file SIU saves — never the original source — and neither one forces a re-encode by itself.

Audio: in PRO mode you can keep just the main track or all of them — handy to compare dubs without downloading the video twice.

Subtitles: choose none, or all the languages the source offers, so you're not left with a pile of tracks you never open.

Smaller file, less cleanup: keeping fewer tracks up front means a lighter result and no extracting or deleting tracks afterwards in another tool.

When it kicks in: if the resolution, FPS or format you picked means the file has to be re-encoded after downloading, SIU can hand that encoding to your GPU instead of loading your CPU.

Nothing to configure: it detects which encoder your card supports (NVIDIA, Intel or AMD) on its own, and falls back to the CPU if there isn't one.

When it doesn't matter: if the file already matches your settings, there is nothing to re-encode, so neither the GPU nor the CPU has extra work to do.

What it does: it raises quiet files and tames loud ones using a broadcast-standard method (EBU R128), so a whole folder plays at a similar level.

The cost: it always re-encodes the audio, so it can't use the instant copy that skips encoding. For one file you won't mix with others, it's often not worth the extra step.

Where it earns its keep: building a playlist from sources mixed at very different loudness, so you're not reaching for the volume knob between tracks.

The idea: the same local AI that splits a track into voice and instrumental lets you keep only the instrumental — a ready-made backing track.

What works best: songs with a clean studio mix. Busy or very compressed recordings can leave traces of the voice behind.

Private and free: it runs on your own PC, with no cloud service and no account involved.

FLAC: compressed without loss — a smaller file with identical audio once decoded. The right pick for keeping and listening long-term.

WAV: raw, uncompressed audio — a bigger file, but the one almost every editing program takes without decoding anything first.

Rule of thumb: going to an editor next? WAV skips a step. Just storing it? FLAC gives the same quality in less disk space.

Where: the trim option in the download panel takes a start and an end time — set them before you press download.

Why it's faster: on a long source (a full concert, a long podcast) you only process the segment you actually want.

Ready to use: the result is already the trimmed clip — no separate cutting step and no second tool.

What it speeds up: the parts that need real processing on your PC (merging, re-encoding). Plain network transfer does not get faster with more threads.

The trade-off: push it high while gaming, editing or running something heavy and you'll feel it everywhere, not just in SIU.

A good habit: leave headroom for the rest of your system, and raise it only when SIU is the main thing your PC is doing.

They share one pipe: every simultaneous download takes a slice of the same connection, so more at once is not free.

Fewer can be faster: on a slower or shared connection, a few downloads finishing quickly can beat many that all crawl.

Separate limits: downloads, GPU encoding and CPU encoding each have their own slider — a slow connection and a busy encoder are two different bottlenecks.

Automatic retries: when a connection hiccups, the download engine retries several times before giving up, so short outages usually go unnoticed.

No babysitting: there is no error to dismiss and no button to press while it recovers.

If it still fails: after a long outage the download is marked as failed, and a single click on retry starts it again.

A toggleable track needs a container built to carry it: MKV handles this natively, while MP4 is more limited depending on the subtitle format.

Burned-in subtitles are painted onto the video itself. Once that's done there is no separate track to carry, so any container works the same.

The question to ask: do you want the viewer to turn subtitles on and off, or switch languages? Only a real track allows that.

MP4 is the safest universal choice: practically every phone, TV and platform plays it without a second thought.

WebM (available in the Convert tab) is a web-oriented format that browsers play natively and that often produces smaller files for web delivery.

When the platform re-compresses anyway (most social networks do), the difference between the two matters far less than it would for a file you keep for yourself.

The log panel: each tab shows a running log of what it is doing. The real reason for a failure — a site refusing requests, a timeout, a missing piece — is usually written there in plain terms.

One link or everything? The log is the quickest way to tell "this one link has a problem" apart from "something is wrong in general" — they need very different fixes.

Reporting an issue: copying the relevant log lines says more in ten seconds than describing what you saw on screen.

Why it happens: sites change their internal structure often, sometimes without warning, and any downloader has to be updated to follow those changes.

What SIU does: it keeps its download engine up to date on its own, and a bigger site change can need a proper app update instead.

How to tell: if only one site fails while everything else works, it is almost certainly that site's change — not a sign that the whole app is broken.