Guides
ガイド
ブラウザ上でファイルを安全に扱うための実践的なガイドとインサイト。各記事から直接ツールへアクセスできます。
How to Watermark a Video — Channel Name or Logo, WYSIWYG
Stamp a copyright line or logo onto a video before sharing it. Position (9 spots), size and opacity adjust with a live preview, and the video is never uploaded.
How to Make a YouTube Thumbnail from Your Video — No Design App Needed
Pause on the best frame of your video, capture it, add a title, and save a 1280×720 thumbnail. Style presets give it structure even without design skills.
How to Merge Audio Files into One — Even with Mixed Formats
Join split voice memos or lecture recordings into a single MP3, in the order you choose. Mixed formats and sample rates are matched automatically, inside your browser.
How to Add Background Music to a Video — Loop, Volume, Fade
Lay music over a silent vlog or timelapse. Short tracks loop automatically to fill the video, and you choose whether to mix with or replace the original sound.
How to Trim a Video — Keep Just the Part You Need (No Quality Loss, Seconds)
Cut the section you need out of a long video. 'Fast' finishes in seconds with zero quality loss; 'Precise' cuts frame-accurately. The video never leaves your device.
How to Reduce Video File Size — Even to an Exact 25MB (In Your Browser)
Practical ways to shrink large videos that keep hitting messenger, email, and upload limits — re-encoded inside your browser, with an honest note on big files.
How to Make a Karaoke Track (Remove Vocals from a Song) with AI, in Your Browser
Make a backing track for karaoke practice or covers. An AI source-separation model runs inside your browser — no upload — and you get the isolated vocals too.
How to Play a Video with SMI or SRT Subtitles (Without Broken Korean Text)
Got a video and a separate SMI/SRT subtitle file? Overlay them in a browser player — it auto-detects the legacy EUC-KR encoding common in Korean SMI files, and lets you nudge sync in 0.5s steps.