FLV to HEIF Converter

FLV to HEIF Converter

FLV is a Flash Video container — a clip made of hundreds of frames over time — and HEIF is a single high-efficiency still image. This tool does not turn the whole video into one image; it grabs one frame from the FLV (the very first frame by default, or any timestamp you set) and saves that single moment as a HEIF, discarding all motion and audio. HEIF stores the frame with the HEVC (H.265) codec at roughly half the size of an equivalent JPEG, so it suits Apple-ecosystem stills where storage matters — but it is not universally openable, so the reference tables below lay out exactly what each format is before you choose.

FLV Format at a Glance

HEIF Format at a Glance

How to Convert FLV to HEIF

1. Upload Your FLV File: Drag and drop your .flv onto the page or click "+ Add Files" to pick it from your device. You can queue several clips; each produces its own still.
2. Pick Frame Selection: Keep "Specific Frame" and set "Time (seconds)" to the exact moment you want — the default is 0, the very first frame. Decimals work, so 2.100 grabs the frame 2.1 seconds in. Or switch to "Multiple Screenshots" to export several frames as separate files.
3. Set Quality Preset and Resolution (Optional): "Quality Preset" defaults to "Very High (Recommended)"; the still keeps the source frame's size under "Keep original" unless you scale it with "Resolution Percentage", a "Width x Height", or cap it with "Specific file size".
4. Convert and Download: Click "Convert" and download your HEIF. No sign-up, no watermark.

Frequently Asked Questions

Does this grab one frame or turn the whole FLV into an image?

One frame. An FLV is a video — hundreds of frames over time — but a HEIF is a single still, so this tool decodes exactly one moment from the clip and saves it. By default that is the very first frame at 0 seconds; set "Time (seconds)" to grab any other moment. All motion and audio are discarded. If you need several stills, switch to "Multiple Screenshots", which returns each captured frame as its own HEIF. If you want to keep the motion instead, convert to an animated GIF.

Is a HEIF frame really about half the size of the same JPEG?

Usually, yes. Apple states that HEIF uses less storage than JPEG at the same visual quality, though it does not publish a fixed percentage (Apple Support). Independent comparisons commonly put a HEIF still at roughly 40–60% of the JPEG size for the same frame, with the gap widening on detail-heavy images. The savings come from HEVC's intra-frame prediction, which is far more efficient than JPEG's 1992-era 8×8 DCT blocks. In our testing, a single frame from a 480p FLV at the Very High preset came out well under 100 KB as HEIF — roughly half what the same frame produced as a Very High JPEG.

Will the HEIF open on Windows, Android, and the open web?

Not everywhere. macOS High Sierra (10.13)+, iOS 11+, and iPadOS decode HEIF out of the box. Windows 10 and 11 need the free HEIF Image Extensions from the Microsoft Store. Many Android gallery and chat apps still re-encode to JPEG on share. In browsers, only Safari 17+ renders HEIF natively — Chrome, Firefox, and Edge have no decoder (caniuse). If the frame needs to open anywhere, save it as a JPG instead, or run HEIF to JPG afterward.

Why won't my FLV frame be high resolution?

Because the source rarely is. FLV was the web-streaming format of the Flash era, and most surviving FLV files are modest-resolution, already-compressed video — often 240p to 480p. A still pulled from one inherits exactly that detail: re-encoding to HEVC won't invent sharpness the original frame never had. Keep "Quality Preset" at Very High or Highest and "Keep original" resolution to preserve whatever detail is there, but a low-res FLV will still produce a low-res HEIF.

Is the conversion lossy, and how do I get a pixel-exact frame?

It is lossy twice over. The FLV frame is already a lossy, compressed image; decoding it and re-encoding as HEVC adds a second lossy pass — fine for a thumbnail, poster frame, or screenshot, but not pixel-exact. Keeping "Quality Preset" at Very High or Highest minimises visible artefacts. If you need a frame with no lossy re-compression, grab it as a lossless PNG instead.

Will the file be .heif or .heic, and are they the same?

They describe the same container. .heic is the standard label when the still is encoded with HEVC (H.265), per ISO/IEC 23008-12; .heif is the more general label. Apple devices and most camera firmware write .heic, and the two are interchangeable on Apple platforms. Windows treats them identically once the HEIF Image Extensions package is installed.

What happens to my files after conversion?

Your FLV is uploaded over an encrypted connection, processed on our servers, and the upload plus the generated HEIF are deleted automatically a few hours after conversion. There is no sign-up, no watermark, and files are never shared or made public.