| The MKV will not import | The container may be corrupted, encrypted or contain an unsupported stream. | Play the source in another media player, try a known-good short file, and check whether the selected source format and codec are supported. |
| Conversion freezes at the start | WebAssembly assets, initialization or large source parsing may exhaust browser resources. | Allow required assets to load, close heavy tabs, try a smaller file and avoid several large simultaneous conversions. |
| An unsupported codec error appears | The FFmpeg build cannot decode the input or encode the selected output codec. | Try an available H.264 preset for delivery or a compatible source; confirm that ProRes or other requested codecs exist in the workbench. |
| MOV downloads but QuickTime will not open it | The MOV may contain an unsupported codec, profile, track or invalid timing. | Choose a conservative H.264/AAC MOV preset, re-encode instead of copying, and test the export again. |
| Final Cut Pro rejects the MOV | The file may lack a codec or audio format accepted by that version of the editor. | Export a short sample using an editing-oriented supported preset and test import before a full batch. |
| Audio is missing after conversion | The chosen track may be incompatible, disabled or absent in the output. | Check source track availability, select supported audio encoding and play the completed MOV with sound. |
| The wrong language track is present | Multi-track MKV sources may default to a different primary audio stream. | Review available audio selection controls, identify the desired source track and retain the original MKV for recovery. |
| Subtitles disappeared | MOV track mapping and subtitle codec support may differ from MKV. | Keep subtitles separately where possible and test captions in the intended player; avoid assuming automatic transfer. |
| Audio and video are out of sync | Variable frame rate, timestamp mapping or speed changes can affect timing. | Try a full re-encode with appropriate frame-rate handling and verify a dialogue segment near the beginning and end. |
| The converted MOV is too large | ProRes, high quality settings or uncompressed audio can require substantial space. | Use H.264/HEVC where compatible, review resolution and quality settings, and avoid unnecessary professional mastering presets. |
| Picture looks blurry or blocky | The selected output bitrate or quality is too low, or downscaling removed detail. | Increase quality, preserve source resolution where useful, and avoid multiple lossy conversion generations. |
| The image is stretched or cropped | A crop, rotation or scaling setting may have changed the aspect ratio. | Reset transformations and choose settings that preserve the original geometry; compare framing after export. |
| Movement appears jerky | Frame-rate conversion or limited encoding performance may produce dropped or duplicated frames. | Try original frame rate, remove unnecessary speed changes and test a simpler encoding preset. |
| Instant remux mode fails | The original streams cannot be legally or reliably packaged inside MOV. | Switch from copy mode to an encoding preset with MOV-compatible video and audio. |
| Batch ZIP is missing a file | One queued job may have failed or the archive was created before all expected outputs were ready. | Inspect individual job statuses, retry failed clips and check extracted filenames and file sizes. |
| Download button produces nothing | Browser download restrictions, full disk or blocked popups may interrupt saving. | Confirm available disk space, browser download permission and completed processing, then retry one file. |
| Browser crashes with a 4K or long video | High-resolution decoding and output buffering can exceed WebAssembly or device memory. | Use a stronger desktop, shorten the clip or reduce conversion workload; keep fewer jobs open at once. |
| Processing is slower than expected | Full transcoding, filters and ProRes can be CPU-intensive in a browser. | Prefer remux where valid, reduce unnecessary filters and let the current job finish before starting another. |
| URL import is blocked or unavailable | Remote servers may deny cross-origin access, require authentication or use unsupported response types. | Download an authorized source locally and select that file; do not bypass access controls. |
| I am unsure whether a sensitive file is private | Local file processing and external page services or URL import can have different data flows. | Read the current privacy policy, verify the exact workflow and follow organizational rules before processing sensitive footage. |