Trim MP4

How to Trim MP4 Video Online

1. Upload Your MP4 File: Drag and drop or click "+ Add Files" to load an MP4 from your device. Batch is supported — every file gets the same trim window or a per-file window. Files process on our servers; no upload account is required.
2. Set Start Time and Duration: Enter the start point in HH:MM:SS.sss (or seconds) and the duration of the clip you want to keep. The output runs from start for duration seconds — millisecond precision is supported, and you can preview the in/out points before processing.
3. Pick Codec and Quality (Optional): Leave Video Codec set to the input (typically H.264 for MP4) to keep encoding fast and preserve quality. Switch to H.265 / HEVC to roughly halve file size at the same visual quality, VP9 or AV1 for web-friendly modern codecs, or MPEG-4 for old-device compatibility. Quality Preset runs Highest → Very High → High → Medium → Low → Very Low; or set a target file size (% or exact MB), a constant bitrate, or a CRF value (0–51 for H.264, 18–28 is the practical range).
4. Resize and Trim and Download (Optional): Pick a Resolution Preset (4K 2160p / 1440p / 1080p / 720p / 480p / 360p / 240p / 144p, plus social presets like 1080×1920 for Reels/Shorts and 1080×1080 for square feeds), scale by percentage, or enter custom width × height. Click Trim and grab each clip individually or as a ZIP.

Why Trim MP4 Files?

MP4 (MPEG-4 Part 14) is the dominant delivery container for H.264 and H.265 video — it plays natively on every modern browser, every iPhone and Android since 2010, and every TV and game console you'll meet in the wild. Trimming an MP4 removes unwanted footage at the start, end, or middle without re-shooting and without exporting from a heavyweight editor. Typical reasons people trim:

• Cut down for short-form social — YouTube Shorts caps at 3 minutes (raised from 60 seconds in September 2024), Instagram Reels cap at 3 minutes, TikTok allows up to 10 minutes, and Twitter/X tops out at 2:20 for non-Premium accounts. Trim a 12-minute screen recording down to the 45-second highlight before uploading.
• Remove dead air at the front of a recording — Zoom, Teams, OBS, and phone recordings usually start with 5–15 seconds of "is this thing on?" and end with people leaving the call. Trimming both ends keeps only the substance.
• Make a clip fit a chat or email cap — Discord's free tier dropped to 10 MB per file in September 2024 (was 25 MB previously); Gmail caps attachments at 25 MB. A 90-second highlight at 1080p H.264 lands comfortably under both; an hour-long uncut recording does not.
• Extract a single segment from a long recording — Lecture, interview, or gameplay sessions are often hours long; trim once per topic to ship focused clips instead of asking viewers to scrub.
• Pre-trim before further editing — Even if you'll cut more in Premiere or DaVinci Resolve, dropping the obvious dead time first means smaller proxies, faster scrubbing, and shorter render times downstream.
• Comply with platform per-clip limits — Storage tiers and some CDNs charge per minute uploaded, not per file; a 45-second highlight ships cheaper than the source.

If you also want to change container or codec, do MP4 to MOV or MP4 to GIF after trimming. For a different output container, see Trim MOV. For dropping file size after trimming, see Compress MP4. The sibling tool Cut MP4 uses the same engine — pick whichever wording matches what you searched for.

Stream-Copy vs Re-Encode — and Which One This Tool Uses

Property	Stream-Copy Trim (-c copy, some desktop tools)	Re-Encode Trim (how XConvert trims)
Quality loss	None — bit-for-bit identical frames	Visually none at the default preset (CRF 18 H.264 / CRF 17 HEVC)
Cut precision	Keyframe-aligned (cuts move to nearest I-frame)	Frame-accurate to the millisecond
Speed	Effectively instant	Proportional to clip length, resolution, codec
Audio sync	Preserved when stream copy is supported	Re-encoded from the same in-point, stays in sync
Codec change	Not possible — must keep source codec	Any supported codec, resolution, or bitrate
Typical keyframe drift	0–10 seconds depending on GOP length	None

x264 and x265 default to a maximum keyframe interval of 250 frames (about 10 seconds at 25 fps and a little over 4 seconds at 60 fps), with the encoder free to place additional keyframes at scene changes. That's why a stream-copy trim in desktop tools may start a few seconds earlier than the timestamp you typed — it snaps to the nearest preceding I-frame because P- and B-frames depend on previous keyframes for their data. XConvert always re-encodes the kept segment at the visually-lossless default preset, so the cut lands exactly where you asked — on a specific word or beat if you want.

Codec and CRF Quick Guide for MP4 Output

Codec	CRF range (lower = better)	Visually transparent	Notes
H.264 (libx264)	0–51 (default 23)	18–20	Universally supported; safest pick for MP4
H.265 / HEVC (libx265)	0–51 (default 28)	22–24	~50% smaller than H.264 at equal quality; iOS and modern Android decode it natively
AV1 (libaom-av1, libsvtav1)	0–63 (default ~30)	25–32	Newest royalty-free codec; best compression but encoder is slower; YouTube and Netflix re-encode to AV1 server-side
VP9 (libvpx-vp9)	0–63 (default 31)	28–33	WebM's native codec; widely supported on the web
MPEG-4 (Xvid / DivX)	1–31 qscale (lower = better)	2–4	Older but still useful for legacy DVD players and very old phones

CRF (Constant Rate Factor) targets a perceptual quality level and lets bitrate vary across the clip. Constant bitrate (CBR) holds a fixed bits-per-second — useful when a delivery platform wants a known size budget, less efficient quality-per-megabyte than CRF for almost any creative video.

Frequently Asked Questions

Will trimming reduce my MP4's quality?

Not visibly. Every trim re-encodes the kept section at the visually-lossless default preset (CRF 18 for H.264 / CRF 17 for HEVC), so the output is not mathematically identical to the source, but the re-encode is visually transparent for nearly all material — you'd need side-by-side comparison on a calibrated monitor to spot the difference. In exchange, the cut is frame-accurate instead of snapping to a keyframe.

Why does my trim start a few seconds before the timestamp I entered?

With XConvert it shouldn't — the trim re-encodes the kept segment, so the output starts exactly at the timestamp you entered. The snap-back you're describing is keyframe alignment in stream-copy tools: MP4s compressed with H.264 or H.265 only store a full image (an I-frame, also called a keyframe) every few seconds, so a tool that cuts without re-encoding must rewind to the previous keyframe for the file to decode. Here the trimmer reconstructs the in-between frames, so no rewinding happens.

Can I trim to exact frame-accurate timestamps?

Yes — every trim is frame-accurate. Enter the start and duration in HH:MM:SS.sss and the encoder decodes from the nearest preceding keyframe up to your in-point, then writes the output starting exactly at your specified frame. Single-frame precision is the default behavior, no special mode needed.

Can I trim multiple sections out of one MP4 in a single pass?

Not in a single output file from this tool — each trim produces one continuous output. If you need to remove a middle section, trim twice (once for the before, once for the after) and join the two with a video joiner. For multi-segment edits with crossfades or transitions, use a non-linear editor.

Does trimming preserve the audio stream and keep it in sync?

Yes. Audio is re-encoded (default AAC) from the same in-point as the video, so the two stay aligned — you should see no audible drift even on hour-long source files. Note the output carries a single audio track: multi-language audio tracks and embedded subtitles are not guaranteed to carry over, so keep the source if those matter.

What happens to MP4 metadata (creation date, GPS, camera model)?

Don't count on it. The trim re-encodes the streams and rewrites the container, so top-level moov atom metadata — creation date, GPS coordinates on iPhone/Android footage, camera make/model — may or may not carry through, and chapter markers generally don't survive. If that metadata matters, archive the untouched source alongside the trimmed clip.

Why is my trimmed MP4 larger than I expected when I only kept 30 seconds?

If you re-encoded to a higher bitrate or a less efficient codec than the source, the output can be larger per-second than the input despite being shorter overall. Check that your CRF or bitrate target is not below the source bitrate — for a 4K H.264 source averaging 50 Mbps, picking a CRF of 18 may write a near-lossless output that's comparable in size to the original. Drop to CRF 23–26, switch to H.265, or set a target file size to shrink the result.

Can I trim very large MP4 files (4K, hour-long recordings)?

Yes. Trims run on our servers — there's no fixed upload cap on the file itself, only upload time over your connection. Processing scales with the length of the segment you keep, not the full source: trimming a 2-minute clip out of a 4K hour-long recording only encodes those 2 minutes.

Is anything uploaded to your servers, and is it free?

Trimming runs on our servers and files are deleted after the session ends. No account, no watermark, no per-file or per-day count caps, and no hidden Pro tier gating duration or resolution.