How to convert h.264 to h.265 and cut the file size roughly in half
- Step 1Check your source's current bitrate — To actually save space you target a bitrate below the source's. A 1080p phone clip is often 15–25 Mbps of H.264; HEVC can match it visually at roughly half. If you don't know the source bitrate, divide file size in megabits by duration in seconds.
- Step 2Open the encoder on a hardware-capable device — Pro + Media plan required, plus a browser exposing a hardware HEVC encoder (Chromium on Windows with NVENC/AMF/QSV, or Safari/Chrome on a Mac). Firefox generally can't and will fail fast.
- Step 3Drop the H.264 file — Accepted inputs include MP4, MOV, MKV, WebM, AVI, M4V, TS. The source must be browser-decodable — standard H.264 always is.
- Step 4Set the target bitrate for the saving you want — Type the kbps figure (the field multiplies by 1000). To halve a ~16 Mbps source, try ~8000 kbps. Leave at
0only if the source is clearly over-bitrated and a resolution-based ceiling is acceptable. - Step 5Leave framerate at 0 unless you need to change it —
0keeps the source cadence. A conversion shouldn't normally change framerate — only set it if you're deliberately normalising VFR footage. - Step 6Encode and compare sizes — Run it (streams to disk on Pro + Media with File System Access, otherwise downloads). Compare input vs output bytes in the result panel. Remember the output is video-only — the size comparison excludes audio.
Why H.264 → H.265 saves space
HEVC's coding tools let it match H.264 quality at a lower bitrate. The saving is realised only when you target a lower bitrate — which is exactly the control this tool exposes.
| Factor | H.264 | H.265 (HEVC) |
|---|---|---|
| Block size | Macroblocks up to 16×16 | Coding tree units up to 64×64 — better on flat areas |
| Prediction modes | Fewer intra/inter modes | More modes — tighter prediction, fewer residual bits |
| Typical bitrate for same quality | Baseline | ≈ 50–60% of H.264 |
| Result | Larger file | ≈ 40–50% smaller at matched quality |
| Decoder support | Universal | Modern only (no Firefox, no pre-2015 hardware) |
Picking a target bitrate from your H.264 source
Practical starting points for halving file size. Set the bitrate field in kbps; it is stored as bits/sec. Adjust upward if motion-heavy content blocks.
| Source (H.264) | Approx source bitrate | Try (HEVC kbps) | Expected size change |
|---|---|---|---|
| 1080p phone clip | ~16–24 Mbps | 8000 | ~half |
| 1080p screen recording | ~6–10 Mbps | 4000 | ~40% smaller |
| 720p webcam / call capture | ~3–5 Mbps | 2000 | ~40% smaller |
| 4K phone / camera | ~45–80 Mbps | 20000 | ~half |
| Already-tight web H.264 | ~2–3 Mbps | set explicitly, test | small gain — HEVC has less to recover |
The two controls (and what's not here)
Everything this tool exposes for a conversion. No CRF, no preset, no audio passthrough.
| Control | Values | Default |
|---|---|---|
| Bitrate (kbps) | 0 (auto) or a kbps number | 0 |
| Framerate | 0 (source) or a forced fps | 0 |
| Audio | Not carried through (video-only output) | — |
| Output | MP4 (-h265.mp4) | — |
| Quality model | Bitrate-driven (no CRF) | — |
Cookbook
Concrete H.264-to-HEVC conversions with the bitrate you'd actually enter and the size outcome to expect.
Halve a 1080p phone video
A 60-second 1080p clip at ~16 Mbps H.264 is ~120 MB of video. Target ~8 Mbps HEVC and you land near half, at comparable quality.
Input: beach.mp4 (1080p, H.264, ~16 Mbps, 60s)
video ~= 16 * 60 / 8 = 120 MB
Fields: Bitrate (kbps) = 8000 Framerate = 0
Output: beach-h265.mp4
video ~= 8 * 60 / 8 = 60 MB (video-only, no audio)Shrink a long screen recording
Screen recordings compress extremely well in HEVC because they're flat and low-motion. You can go aggressive on bitrate.
Input: demo.mp4 (1080p screen rec, H.264 ~8 Mbps, 10 min) Fields: Bitrate (kbps) = 3000 Framerate = 0 Why low works: flat UI regions cost few bits in HEVC. Output: demo-h265.mp4 (~40% the original video size)
Auto bitrate on an over-bitrated source
If the source is clearly carrying more bits than it needs, auto (0) already shrinks it via the resolution-based ceiling — no need to compute a target.
Input: export.mp4 (1080p, H.264 at 30 Mbps — overkill) Fields: Bitrate (kbps) = 0 Framerate = 0 Auto target ~= 1920*1080*0.06 bps (a ceiling) HEVC realtime encode lands well under 30 Mbps -> smaller file
Don't lose the audio by accident
The conversion is video-only. If your H.264 had a soundtrack you care about, the HEVC output won't have it — plan for that.
Before: lecture.mp4 (H.264 video + AAC audio) After: lecture-h265.mp4 (HEVC video, SILENT) If you need a smaller file WITH audio instead, use: /video-tools/video-bitrate-set (sets video+audio kbps) /video-tools/discord-compressor (size-target, keeps audio)
Source won't load — transcode first
If the H.264 is wrapped in a container or pixel format the browser can't decode (rare for plain H.264, common for odd MKV/AVI), convert to a standard MP4 first, then HEVC-encode.
Error: "Could not load source video."
Step 1: /video-tools/video-transcoder -> MP4 / H.264
Step 2: this tool -> HEVC
Reason: frames are pulled from a browser <video> element,
so the source must be browser-decodable.Edge cases and what actually happens
File didn't get smaller
Bitrate too highIf you left bitrate on auto and the source was already tightly encoded, the auto ceiling can exceed the source bitrate and the file stays the same size or grows. Set the bitrate explicitly below the source's to guarantee a saving.
Audio disappeared after conversion
By designThe hardware encode path is video-only — H.264 audio is not transcoded into the HEVC MP4. Use a size/bitrate tool that preserves audio, such as video-bitrate-set, if you need a smaller file with sound.
No hardware HEVC encoder
Encode failsOn Firefox or a GPU without HEVC encode, the run throws "Hardware encoding for H265 is not available on this device." For a software conversion, use the video-transcoder with codec H.265 (CRF-controlled libx265 WASM).
Tight low-bitrate target blocks on motion
Quality dropBecause there's no CRF, an aggressive bitrate produces visible artefacts on motion. Raise the kbps, or switch to the video-transcoder and use CRF to hold quality while letting size float.
Free or Pro plan
Upgrade requiredThe tool is gated to Pro + Media. Free (1 GB) and Pro (10 GB) see the file-size cap in the dropzone but hit the upgrade overlay on run.
AV1 would be even smaller
Consider AV1If your hardware supports AV1 encode (RTX 40-series, Intel Arc, Apple M3+), AV1 is roughly 30% smaller again than HEVC and royalty-free. See the av1-encoder.
4K source on a phone
OOM riskRe-encoding a large 4K H.264 on a mobile browser can exhaust the WASM heap. Do 4K conversions on a desktop with a hardware encoder.
Output plays on Mac but not in Firefox
Decoder supportThe HEVC MP4 is valid; Firefox just doesn't decode HEVC. For broad distribution keep an H.264 copy via the web-optimizer.
Frequently asked questions
How much smaller will my file get?
Typically 40–50% at matched quality, but it depends entirely on the bitrate you target. The saving is realised by setting a target bitrate below the source's — HEVC just lets you do that without losing visible quality. If you leave bitrate on auto, the saving depends on how over-bitrated the source was.
Will the quality look the same?
At an equivalent bitrate, HEVC looks as good or better than H.264 — that's the codec's whole advantage. The risk is going too low on bitrate: because there's no CRF here, an aggressive target can show blocking on motion. Start from the table's suggestions and nudge the bitrate up if you see artefacts.
Why can't I just set a CRF like in HandBrake?
This tool uses your GPU's hardware encoder via WebCodecs, which is bitrate-controlled, not CRF-controlled. So you set a target bitrate instead. If you specifically want CRF behaviour, use the video-transcoder with codec H.265, which runs libx265 in WASM and accepts a CRF value.
Does the conversion keep my audio?
No — the output MP4 is video-only. The H.264 audio track is not transcoded into the HEVC file. If you need a smaller file with audio, use video-bitrate-set or one of the size-target compressors instead.
What's the output format?
An MP4 named <yourname>-h265.mp4 containing an HEVC video stream. There's no choice of container on this tool.
Is my video uploaded anywhere?
No. The H.264 source is decoded, re-encoded on your GPU, and muxed to MP4 entirely in the browser tab. Only an anonymous usage counter is recorded server-side.
It failed saying hardware encoding isn't available — what now?
Your browser doesn't expose a hardware HEVC encoder. Use a Chromium browser on a machine with NVENC/AMF/Quick Sync, or a Mac with VideoToolbox. For a software conversion that works anywhere, use the video-transcoder with codec H.265.
Should I use auto bitrate or set it myself?
Set it yourself for a predictable saving. Auto targets roughly width × height × 0.06 bps, which acts as a ceiling — it shrinks over-bitrated sources but may not save much on an already-tight file. To halve a known source bitrate, target about half of it.
Can I convert several files at once?
Yes on Pro + Media (up to 50 per job) or Developer (unlimited). They process sequentially and each output keeps its source name with the -h265.mp4 suffix.
Would AV1 save more than HEVC?
Yes, by roughly another 30% at the same quality, and AV1 is royalty-free — but only if your hardware can encode it (RTX 40-series, Intel Arc, Apple M3/M4). See the av1-encoder. Decoder support for AV1 is also broad in modern browsers, unlike HEVC.
Why did my file get bigger?
Almost always because auto bitrate set a ceiling above the source's actual bitrate, or because you typed a kbps higher than the source. Set the bitrate explicitly below the source rate.
Will the HEVC file play everywhere?
On modern Apple devices, Windows with the HEVC codec, recent Android, and most Smart TVs — yes. Not in Firefox and not on old hardware. For maximum reach, keep an H.264 copy for distribution and use HEVC where you control the player.
Privacy first
Every JAD Video tool runs entirely in your browser via WebCodecs and FFmpeg (WebAssembly). Your video files never leave your device — verified by zero outbound network requests during processing.