To make a video slow motion on iPhone, use either the built‑in Slo‑Mo mode in the Camera app when recording, or slow it down later in the Photos app or iMovie. Below is a clear step‑by‑step guide plus some quick tips.

Record in Slo‑Mo (best quality)

Use this when you know in advance you want slow motion.

  1. Open the Camera app.
  2. Swipe through modes until you see Slo‑Mo.
  3. Frame your shot, then tap the red Record button.
  4. Tap the red button again to stop.
  5. Open Settings → Camera → Record Slo‑Mo to choose a higher frame rate (like 120 fps or 240 fps) for smoother slow motion.

Change Slo‑Mo speed and section

For clips recorded in Slo‑Mo, you can choose which part is slow and which is normal speed.

  1. Open Photos and tap your Slo‑Mo video.
  2. Tap Edit (top right).
  3. At the bottom timeline, you’ll see vertical lines:
    • Dense lines = slow motion
    • Sparse lines = normal speed
  4. Drag the two taller handles inward or outward to choose where slow motion starts and ends.
  5. Tap Done to save.

Make an existing video slow motion (Photos & iMovie)

If you shot a normal video, you can still slow it down a bit (though it won’t look as smooth as true high‑fps Slo‑Mo).

Option 1: Photos app (limited)

  • Open Photos → your video → Edit.
  • Some iOS versions let you adjust speed if it was originally Slo‑Mo; for regular videos, this is limited, so use iMovie for better control.

Option 2: iMovie on iPhone

  1. Open iMovie and tap Create Project → Movie.
  2. Select the video and tap Create Movie.
  3. Tap the clip in the timeline so it’s highlighted.
  4. Tap the Speed icon (little speedometer).
  5. Drag the slider left to slow the video down (e.g., 0.5×, 0.25×).
  6. Play to preview, then tap Done and Share/Save Video to export back to Photos.

Quick tips for smoother slow motion

  • Record in Slo‑Mo with the highest frame rate your iPhone supports (in Settings → Camera → Record Slo‑Mo) for less choppy slow motion.
  • Use good light ; slow‑motion needs more light to look clean.
  • Avoid very fast panning; keep the phone steady and let the subject move.
  • For dramatic effect, slow down only a short key moment (a jump, a splash, a spin) and leave the rest in normal speed.

“Quick Scoop” recap

  • Use Camera → Slo‑Mo for the best, smooth slow‑motion results.
  • Fine‑tune which part is slow in Photos → Edit by dragging the slow‑motion handles.
  • Turn normal videos into slower clips with iMovie’s Speed slider.
  • Higher frame rate + good lighting = cleaner, more cinematic slow motion.

Note: Information gathered from public guides and tutorials on iPhone slow‑motion recording and editing.