iOS users like to use their iPhone, iPad or iPod touch to shot videos. When you have captured some lengthy videos, how to crop parts of a video in iPhone camera roll? Can you trim or crop a video directly on iPhone without any third party video editors or apps? Yes, iOS 7 users can cut any videos in Camera Roll without iMovie or any other video cutter or apps. Check out below steps to split your long videos into short parts or segments. If you are using an iPad, see this page: trim/crop videos in Camera Roll on iPad.
Cut Videos on iPhone
1. Open Photos app on iPhone or switch to Camera Roll form the default Camera app.
2. Find the video you need to cut. Tap on it to select it. The video then opens in full screen. See below screenshot.

3. Press on the left or right of the video play slider above the video. You can slide it from left to right to select the starting point, or slide from right to left to choose the ending frame of the video.

4. You should see a Trim button from the top right corner. Tap on it, you will get a dialogue, prompting you options to save as new video clip or overwrite original video clip. Confirm the save option, your Camera Roll video will be cut and saved to Camera Roll.
Note: If you choose Trim Original, the output video will replace the original one. So if you are not sure of it, always select Save as New Clip to export the video as a new copy without deleting the original one.
The instructions above apply to various iPhone models and iOS versions, like iPhone 4s, iPhone 5, iPhone 5s, iPhone 5c, iPhone 6, iPhone 6 plus, iOS 6, iOS 7, iOS 8, etc.
By cutting long video, you can dump those unwanted parts of a video and save only your favorite sections. Short video clips are much easier to be shared over the web, for example, you can upload them to Vimeo, Youtube and other video sharing service. Plus it can also free up a lot of space on iPhone. Although iPhone allows you to cut videos into short clips, however you will need a video converter in order to join multiple video clips into one. This guide shows you how to merge multiple iPad or iPhone video clips.



Well, unfortunately on my Iphone 6S+, it works up to point 2 above but without the video view slider?? The video view slider appears only when I want to forward the video to Twitter. There, the slider becomes reckless when trimming. It takes a video space of 20 seconds or so and trims itself without your control.
I do not have an iPhone 6s+. Just tried on an iPad which is running on iOS 9.2. Now you can’t see the video view slider until you hit the Edit button at the top right corner of iPad. On the iPhone, this Edit button may be found in different place.
SOMEONE HELP I ACCIDENTLY CROPED IT WOTHOUT SAVING THE ORIGANAL VID AND I WANT TO GET IT BACK
you can try this solution to recover lost videos on iPhone.