Subfast: Subtitle & Captions

Animated captions for any video — zoom effects, karaoke word-highlight, 19 languages. Export SRT, VTT, or burned-in MP4. 100% on-device. 7-day free trial, no card needed.

Subfast adds captions and zoom effects to any video on your iPhone — entirely on-device, without uploading a single byte.

Pick a video from Photos or Files. Add caption cues at precise timestamps, type your text, and export as SRT, VTT, or burn them directly into a new MP4. Add zoom moments anywhere on the timeline — a smooth 3-second zoom-in/out animation plays when the video reaches that point. Everything stays on your phone. No cloud, no upload. Sign in with Apple to start your free trial.

WHAT YOU CAN DO

• Caption any video — MP4, MOV, anything iOS can read • Add caption cues manually — type text, set precise start and end timestamps • Add zoom moments — a 3-second zoom animation triggers at any point you choose • Highlight every word as it's spoken, karaoke-style • Edit transcript text and timing in a clean inline editor • Export as SRT, VTT, plain text, or burn captions directly into a new MP4

PRIVATE BY DESIGN

Other subtitle apps upload your video to their servers. We don't. We can't. Apple's on-device frameworks handle every step locally — the same chip that runs your camera and Face ID is doing the work. That means:

• Subfast works on a plane, in a tunnel, anywhere • Sensitive footage stays sensitive • Sign in with Apple to start your free trial

ZOOM EFFECTS THAT POP

Tap anywhere on the timeline to drop a zoom moment. When your video reaches that timestamp, Subfast plays a smooth 3-second zoom-in/out animation — the same punchy effect that makes short-form content stop the scroll. Add as many zoom moments as you want throughout your clip, then export to MP4 with everything baked in.

BUILT FOR CONTENT CREATORS

Burn captions into your vertical clip in seconds — no re-export, no extra app. Pair captions with zoom moments to punch up high-energy scenes. Export industry-standard SRT and VTT for editing in Final Cut, DaVinci, or CapCut.

BUILT FOR SOCIAL VIDEO

Going viral on TikTok, Instagram Reels, or YouTube Shorts starts with captions. Subfast burns captions into your vertical clip in seconds — no re-export, no extra app. Add zoom moments to punch up the high-energy parts and keep viewers watching.

Podcast creators and video bloggers can subtitle their clips, export a clean SRT or VTT file, and drop it into any editing timeline — without leaving their workflow.

BUILT FOR ACCESSIBILITY

Closed captions for personal video collections that don't have any. Dynamic Type-friendly UI. VoiceOver throughout.

PRICING

Subfast is free to try for 7 days — no payment method required to start.

Subscriptions auto-renew until cancelled. You can cancel anytime in iOS Settings → Apple ID → Subscriptions. Your free trial does not auto-convert to a paid subscription unless you actively subscribe.

Payment will be charged to your Apple ID account at the confirmation of purchase. Subscriptions automatically renew unless auto-renew is turned off at least 24 hours before the end of the current period. Your account will be charged for renewal within 24 hours prior to the end of the current period at the chosen plan's price. Subscriptions can be managed by the user, and auto-renewal may be turned off, by going to the user's Account Settings after purchase.

Privacy Policy: https://subfastapp.vercel.app/en/privacy Terms of Service: https://subfastapp.vercel.app/en/terms