Someone sent you a video that's too long. You need the first 30 seconds.
You don't have video editing software. You don't want to download video editing software. You definitely don't want to pay for video editing software to trim one clip.
Go to 123apps. Upload the video. Trim it. Download it. Done in two minutes.
123apps is a collection of free browser-based tools that handle almost every file task normal people actually need. Not professional post-production. Not enterprise document management. The stuff you need once a month and never have the right software for.
Audio tools: trim an MP3, merge two audio files, convert between formats, change the pitch, remove vocals, record from your microphone, cut a ringtone. Video tools: trim, convert, compress, extract audio from a video, change the format, grab a still frame. PDF tools: merge PDFs, split a PDF, compress a PDF, convert Word to PDF, convert PDF to Word, rotate pages, extract images. File conversion: convert almost any format to almost any other format.
All of it runs in your browser. You upload your file, the tool does the work on their servers, you download the result. Nothing installs on your computer. No account required. No watermark on the output. No "free trial" that stops working after one use.
The tools aren't as powerful as professional software. They don't need to be. They're fast, they work, and they're there when you need them — which is usually when you don't have time to figure out anything else.
Bookmark this one. You'll need it sooner than you think.