How to Upscale Video to 4K Free in Your Browser (No Upload)

• How to use it
• Old formats
• Quality tiers
• Before and after
• The engine
• FAQ
• Cloud version

1. How to use it

1. Choose a clip.

   MP4, MOV, M4V, MKV, WebM or 3GP, up to 2 GB, any length; AVI, MPG, VOB, WMV, FLV, DV, a camcorder's MTS and the other old formats open too — the page turns them into an MP4 first. The browser reads the clip's resolution, frame rate and length on your device and opens the workbench in place of the drop box. A file this browser cannot open or decode is named the moment you choose it, with the way on: the browsers that open it as it is, or a conversion to MP4 (H.264). If a run later finds the file can no longer be read, the panel asks for it again: with Replace, or on an Android phone — whose gallery can stop letting the browser read a video — from Files.

   

2. Pick a size and a quality, preview, start.

   A platform button (YouTube, TikTok · Shorts · Reels, Instagram, X) fills in the shape, size, file type and frame rate that platform wants. "Preview this frame" runs a short test on the frame you paused on and shows it before and after, with the time estimate; under Start the panel names the setting it recommends for this clip, and its time, one tap away. Then press Start; you can pause and resume, a long run saves its progress as it goes, and a long job offers a 30-second trial first.

   

3. Compare and download.

   The original sits on the left and the result on the right — same frame, same moment — with a magnifier that shows the same window of both at the result's pixels. Download as MP4, MOV, MKV or WebM with the sound, copied or re-encoded for the format — where this browser cannot carry it into the format you chose, the panel says so before you start. The file size (the video bitrate) is a setting: Smaller, Standard or Larger — about 17.1 / 34.2 / 54.7 Mbit/s for 4K H.264 — or a rate you type (1–100 Mbit/s), and the panel shows the megabytes before you start. Once a run is done, "Export again" rewrites the file in another size, format, container or frame rate from the frames you already have — no second upscale. The result stays in this browser for 24 hours: within that time, "View" under "Choose video" on the home page opens it here again, to play, compare and download. Open the tool when you are ready.

   

Screenshots: Komekami! Girl's PV (2026), official channel — CC BY 4.0 via Wikimedia Commons, re-encoded at 220 kbit/s.

Any length — long videos welcome, saved as it goes

• Any length

  no cap on the clip — a two-hour film runs the way a ten-second one does, from a file of up to 2 GB

• 15 s

  of graphics work before the first finished piece is on disk, then one every 30 s

• 24 h

  an unfinished run waits for you — the home page offers to continue it from the last saved piece, frame for frame

The result streams into your browser's private storage while the run goes on, in finished pieces — which is what lets a long video, a full movie or an hour-long recording, run through. A job the estimate puts past 90 seconds gets its first piece after 15 seconds of graphics work, and one more every 30 seconds after that; once that first piece is saved, the panel says the run can be continued after a reload. Close the tab, lock the phone, come back within 24 hours: the home page lists the job, picks it up from the last saved piece frame for frame, and joins the pieces into one file at the end. Shorter jobs run straight through in one piece. You can take the whole clip, a window of 5 seconds to 10 minutes dragged on the filmstrip, or one that ends where you type; the estimate next to Start gives the time on your own device, a long job's panel says how much room it needs and offers a 30-second trial first, and where the browser measures its free space, the page checks the result fits before any graphics work starts.

Old formats: AVI, MPG, VOB, WMV, FLV and camcorder files

Camcorder files open as they are. The MTS / M2TS of an AVCHD camera and TS recordings are rewrapped as MP4 inside the page before the workbench shows them — the pictures copied, not re-encoded, and a Dolby Digital (AC-3) sound track turned into AAC (Opus in Firefox) so every browser plays it; a bar in the drop box shows how far it is, and nothing is uploaded. Most camcorder and TV footage is interlaced, and the panel says so: it is upscaled with its fields as they are, so moving edges can show fine comb lines. Try a short window first, or deinterlace it in HandBrake (step 3 below) for the cleanest result.

DVD rips and older downloads come in containers and codecs that browsers do not read — AVI (often DivX or Xvid), MPG and VOB (MPEG-2), WMV, FLV and DV, and the Motion JPEG of old cameras' AVI and MOV files or the MPEG-4 and H.263 of old phones' 3GP. The page converts such a file into an MP4 inside your browser with FFmpeg's own decoders, fetched the first time you choose one, deinterlacing interlaced pictures on the way, and nothing is uploaded: the beginning opens within seconds — enough to preview it and try a short run — while the rest is prepared behind the workbench, and a run of the whole video starts once it is ready; an AVI or FLV that holds H.264 has its video copied into the MP4 untouched. In a browser without WebAssembly these formats still need a conversion first, and the page says so the moment you choose one. Convert such a file once to MP4 (H.264) at its own size, then upscale the MP4:

1. Open the file in HandBrake — free and open source, for Windows, macOS and Linux (for a DVD, open its VIDEO_TS folder).
2. Keep the preset it opens with, Fast 1080p30: it writes an H.264 MP4 and keeps a video smaller than 1080p at its own size. For footage at 50 or 60 frames per second, set Video → Framerate to Same as source.
3. For a DVD, a tape or a camcorder recording, check that Filters → Deinterlace is on: interlaced video shows combed stripes on anything that moves, and an upscale would sharpen them.
4. Start the encode, then choose the MP4 on the home page.

A file that plays in one browser and not in another — an iPhone's HEVC in Firefox — needs no conversion: the page names the browsers that open it as it is. An MKV opens in Safari too, rewrapped the same way.

Which settings for which video

Starting points from our own test footage; the preview decides for your clip. Every row opens the tool with those settings.

How long it takes

Time is frames × time per frame: one minute of clip at 30 fps is 1,800 frames. The estimate next to Start is measured on your own device — the settings the clip opens with, every other setting converted from that measurement by the work it takes — and is the one to trust. Under it the panel recommends a setting for the clip: Pro at the largest size it runs, when that finishes within 8× the clip's length — or within 5 minutes for a short clip — and Fast otherwise; Ultra is never the recommendation, and a phone's is Fast. A setting past 5 minutes names a quicker one that saves at least 30 % of the time, and the recommended one, each one tap away. For scale, on an Apple M4 laptop:

A flagship Android phone (Adreno 750) takes about 5× as long on Fast — about 4.5 min per minute of 1080p clip to 4K — and slows further as it warms up; a mid-range phone a few times more. A gaming PC with a recent NVIDIA or AMD card should be in the laptop's range or quicker; a laptop with built-in graphics sits between the two.

Asking an AI about your settings

The icons after "Can it run?" open ChatGPT, Gemini or Claude with your device, clip, settings and estimate already typed in (the Copy icon puts the same text on the clipboard for any other assistant); the text links this guide, so the answer comes from the long version, not a guess.

Links that carry settings

A link to this site can name the settings to start from — https://4kvideoupscaler.com/?quality=pro&size=2k opens the page with Pro and 2K ready (the rows above and an assistant's answer link this way); what the device cannot run falls back to what it can, and a link never starts a run.

2. Quality tiers

The repair tiers on a phone. Pro and Ultra are 4× restoration networks, and every frame is a long stretch of work for the graphics chip. On a phone that adds up: even on a flagship, a 30-second 720p clip keeps the graphics chip working for about 27 minutes with Pro and 50 with Ultra, and runs that heavy can make the browser switch the graphics chip off. That is why a phone gets Pro on clips up to 480p and Ultra runs on computers; Fast is unaffected.

No tier interpolates frames (frames are only dropped), deinterlaces (the page does that to the old formats as it converts them, before any tier runs), restores faces or changes colour and exposure; each frame is processed on its own, and the optional "Steady" filter under More options only settles grain that flickers in still areas.

3. Before and after

Three real runs of this page's own engine, one per tier, from low-resolution sources: the same window of the same seconds, the source on the left the way a player shows it, the result on the right. Drag the axis.

4. The engine: SR Engine

• 3.0×

  faster than the open-source engine we ran before — same network, same machine: 21.1 ms against 63.3 ms per 1080p → 4K frame

• 546 MB

  of graphics memory for the 720p → 4K second step, or a 128 MiB budget in 4 bands; about 1.36 GB before

• 3 KB

  the smallest model file, 2.4 MB the largest — fetched once per tier, no machine-learning runtime to download

Against the engine we ran before

5. Cloud version

Cloud access

Your email: —
What you tried locally, and what was missing: —
Footage: type · resolution · length: —

Page: https://4kvideoupscaler.com/how-it-works

Your address is used to contact you about cloud access and for nothing else (privacy policy).