Video Converter - Convert Any Video Format Free

Why You Are Here: Five Problems Video Converters Solve

People arrive at a video converter with one of five frustrations. Knowing which one applies to you will help you choose the right format and avoid converting twice.

• Video will not play on the TV. You copied an MKV or FLV file to a USB stick and the smart TV shows nothing, or it plays audio but no picture. The TV does not support the container or the codec inside it.
• iPhone video will not open on Windows. iPhones record in HEVC (H.265) inside a MOV container. Windows 10 and 11 require a paid codec extension from the Microsoft Store to open these files. Without it, the file appears broken.
• File is too large to upload. TikTok caps uploads at 500 MB. WhatsApp compresses anything over 16 MB. Instagram Reels has a 4 GB ceiling but still re-encodes heavily. The original file from your camera or screen recorder often exceeds these limits.
• Downloaded MKV or FLV file will not open. MKV is not natively supported on iPhone or many smart TVs. FLV requires Flash Player, which was permanently retired in December 2020. These files need to be converted to a modern container.
• You want a smaller file without buying software. Modern codecs like H.265 and AV1 can cut file size by 40 to 60 percent at the same visual quality. Converting from an older codec to a newer one achieves this without expensive software.

The Container vs Codec Trap (Why Renaming the File Does Not Work)

This is the single most important concept in video compatibility, and almost no one explains it clearly.

A video file has two separate layers:

• The container is the outer box. It is the file extension you see: MP4, MKV, MOV, AVI. The container organises the video stream, audio stream, subtitles, and chapter markers into one file.
• The codec is how the video data inside that box is compressed. Common video codecs are H.264, H.265 (HEVC), AV1, and VP9. The codec is invisible in the file name.

Think of it like a shipping box. The box shape (container) tells you how it was packed and labelled. But what matters for the recipient is what is inside the box and whether their equipment can handle it (codec).

Why renaming .mkv to .mp4 does not fix anything

If you rename a file from video.mkv to video.mp4, you have only changed the label on the box. The data inside is unchanged. The device still has to decode the same H.265 stream, the same audio track, and the same subtitle format. If it could not do that before, renaming does nothing.

Why an MP4 can still fail on Windows

MP4 is a container. It can hold H.264, H.265, or AV1 video inside. An MP4 file containing H.265 will fail on Windows unless the HEVC Video Extensions codec is installed. The file extension says MP4, but the codec inside is not supported. This surprises many people because they assume MP4 always works everywhere.

The fix

True conversion re-encodes the video data. The file is decoded from the source codec and re-encoded into the target codec inside a new container. This is what a video converter does. Renaming does not re-encode anything.

Codec Comparison: H.264 vs H.265 vs AV1 vs VP9

Choosing a codec affects file size, quality, and which devices can play the result. Here is a practical comparison.

Practical takeaway: If you are sharing a video and you do not know what device will play it, always convert to MP4 with H.264. It is the only codec with truly universal support across every generation of device.

Device Compatibility Matrix

This table shows which format and codec combinations play natively on common devices without installing extra software or apps.

Reading this table: If you see more than two No entries in the row for your current format, convert to MP4 H.264. It is the only row with Yes across every column.

Platform Upload Requirements

Social media platforms are strict about video specs. Using the wrong format means the upload will fail or the platform will re-encode your video and reduce quality further.

YouTube

• Accepted formats: MP4, MOV, AVI, WMV, MKV, WebM, and others
• Recommended: MP4 with H.264 video and AAC audio
• Max file size: 256 GB (verified accounts)
• Max length: 12 hours
• Practical note: YouTube re-encodes every upload to VP9 and AV1 for delivery. Your upload quality is the ceiling for what viewers receive. Upload at the highest quality you have.

TikTok

• Required format: MP4 or MOV
• Recommended codec: H.264
• Aspect ratio: 9:16 vertical (1080 x 1920) for full screen
• Max file size: 500 MB on mobile, up to 2 GB on web
• Max length: 10 minutes
• Practical note: TikTok re-encodes aggressively. Upload at 1080p minimum. Anything below 720p will look poor after re-encoding.

Instagram Reels and Feed Video

• Required format: MP4
• Required codec: H.264
• Aspect ratio: 9:16 for Reels, 1:1 or 4:5 for feed
• Max file size: 4 GB
• Max length: 90 seconds for Reels
• Practical note: Instagram does not accept MKV, AVI, or WMV. If your upload fails, check the format first.

WhatsApp

• Format: MP4 strongly preferred
• Max file size when sent as video: 16 MB
• To avoid compression: Send the file as a Document (paperclip icon) instead of as a video. WhatsApp compresses videos sent as media but sends Documents without re-encoding. The recipient will need to manually open it in a video player.
• Practical note: For anything over 16 MB, convert to MP4 H.264 first, then send as a Document to preserve quality.

Vimeo

• Recommended format: MP4 with H.264
• Max file size: 500 MB on free plans, up to 10 GB on paid plans
• Practical note: Vimeo preserves source quality better than most platforms. Upload the highest quality source you have.

Format-Specific Insights

Each format has one practical thing you need to know -- not a definition, but what actually matters when you are deciding whether to keep it or convert it.

MP4 -- The Container, Not the Quality Level

MP4 is a container format, not a quality standard. An MP4 file recorded on a cheap phone looks different from one recorded on a cinema camera. The visual quality depends entirely on the codec inside (H.264, H.265, or AV1) and the bitrate used. When someone tells you to send an MP4, they mean the container. They are not telling you anything about quality. If your MP4 fails to play on a device, check what codec is inside it before assuming the format is the problem.

MKV -- Designed for Local Playback, Not Device Compatibility

MKV was designed to store high-definition movies with multiple audio tracks, subtitle tracks, and chapter markers. It is excellent for this purpose. However, it was never designed for cross-device compatibility. iPhones cannot play MKV natively, most smart TVs do not support it, and gaming consoles do not recognise it. If you are trying to play an MKV file on anything other than a desktop media player like VLC, convert it to MP4 H.264. The video quality inside the MKV will be preserved during this conversion -- you are only changing the container.

MOV -- The iPhone Problem on Windows

iPhones since the iPhone 7 record video in H.265 (HEVC) by default and save it as a MOV file. MOV is an Apple container and H.265 is a modern codec. Windows 10 and 11 do not include an H.265 decoder. The result is that iPhone videos sent to a Windows user appear broken or will not open in the default Photos app or Media Player. The paid HEVC Video Extensions codec from the Microsoft Store (approximately USD 1) fixes this, but most recipients do not have it. The permanent fix is to convert MOV to MP4 H.264 before sharing. Alternatively, on your iPhone go to Settings > Camera > Formats and change from High Efficiency to Most Compatible. This makes the camera record H.264 instead of H.265, which is universally compatible but produces larger files.

AVI -- No Modern Use Case for Keeping It

AVI (Audio Video Interleave) was introduced by Microsoft in 1992. It does not support modern codecs efficiently, has poor streaming performance, and produces unnecessarily large files compared to MP4 with H.264 at the same quality. The only reason to have an AVI file today is because it came from an old device, old recording software, or an old archive. There is no reason to keep creating or saving in AVI format. Convert to MP4 H.264 and you will get the same quality in a smaller file that plays on everything.

WMV -- Losing Support Rapidly

WMV (Windows Media Video) is a proprietary Microsoft codec that was widely used in the early 2000s. It plays natively on Windows but has virtually no support anywhere else. Samsung removed WMV support from its smart TV firmware in 2025. iPhones, Android devices, and macOS do not support it without third-party apps. If you have WMV files you want to preserve or share, convert them to MP4 H.264 now. The longer you wait, the more devices will stop supporting it.

FLV -- Flash Is Permanently Dead

FLV (Flash Video) was the dominant web video format from approximately 2005 to 2015. Adobe Flash Player was the required plugin to play FLV files in a browser. Adobe permanently retired Flash Player on 31 December 2020. No major browser supports Flash. No new device includes a Flash Player. FLV files are completely unplayable on any modern system without a dedicated media player application. If you have FLV files, convert them to MP4 immediately. There is no scenario where keeping them in FLV format is beneficial.

WebM -- Excellent for Browsers, Limited Elsewhere

WebM was created by Google as an open-source web video format. It works natively in Chrome, Firefox, and Edge. Android supports it. However, WebM has no native support in iPhone Safari (iOS), macOS QuickTime, Windows Media Player, smart TVs, or game consoles. If you are embedding a video on a website, WebM is excellent -- smaller files and royalty-free. If you are sharing a video file with someone, do not use WebM. They will likely be unable to open it without a third-party player. Convert to MP4 for sharing.

3GP -- Legacy Mobile Format

3GP was designed for 3G mobile networks in the early 2000s. It uses very low bitrates and resolutions (typically 176 x 144 or 320 x 240). If you have a 3GP file, it was recorded on an old feature phone. Converting it to MP4 will not improve its resolution or quality -- that information was never captured. But converting to MP4 H.264 will make it playable on modern devices, which may not recognise the 3GP container at all.

M4V -- The DRM Complication

M4V is an iTunes container used for video purchased or rented from Apple. It is nearly identical to MP4 with one significant exception: M4V files purchased from iTunes are DRM-protected (Digital Rights Management). DRM-protected M4V files cannot be converted to any other format by any converter, including this one. If you try to convert a purchased iTunes movie, the conversion will fail or produce a blank output. M4V files you recorded yourself or imported into iTunes without DRM can be converted normally.

Generation Loss: Why You Should Always Convert From the Original

Video codecs like H.264, H.265, and AV1 are lossy. When a video is encoded, some visual information is permanently discarded to achieve a smaller file size. When you convert a video that is already encoded in a lossy codec, the process is:

1. Decode the compressed video (some quality already lost from original recording)
2. Re-encode into the new codec (more quality lost in this step)

Each re-encode from a lossy source compounds the quality loss. This is called generation loss. The effect is often subtle on the first conversion but becomes visible after multiple conversions as softness, blocking artefacts, or colour banding.

Practical rules to minimise generation loss

• Always convert from the original source file. If you recorded a video on your phone, convert the original file from the camera roll, not a copy that was already sent through WhatsApp or uploaded to Instagram (both of which re-encode heavily).
• Do not convert the same file multiple times. Decide on your target format once and convert directly from the source.
• Lossless intermediates exist for editing. If you are editing video professionally, use ProRes or DNxHD as an intermediate format during editing. These are designed for repeated encode/decode cycles. Convert to H.264 or H.265 only at the final export step.
• You cannot recover lost quality. Converting from a heavily compressed 720p file to H.265 will give you a smaller file, but it will not restore detail that was not in the source. Resolution cannot be increased by conversion.

Decision Guide: Which Format Do You Need?

Use this guide to find the right conversion for your situation without reading the entire page.

My video will not play on my device

My upload is failing or being rejected

Specific situations

• iPhone video will not open on Windows: The file is MOV with H.265. Convert to MOV to MP4 using H.264. Or on iPhone: Settings > Camera > Formats > Most Compatible.
• MKV plays on VLC but not on TV: Convert to MP4 H.264. The MKV container is the problem, not the video content inside it.
• FLV file from old download: Flash is retired. Convert to MP4 via FLV converter.
• Need to reduce file size significantly: Convert to MP4 H.265 if your audience uses modern devices (iPhone 7+, Android 8+, newer TVs). Be aware Windows users may need the HEVC codec extension.
• Embedding video on a website: Use WebM as primary with MP4 H.264 as fallback. Most website builders accept both via the HTML5 video tag.

Supported Video Formats

ChangeMyFile converts between all major video formats:

• MP4 - Universal standard, plays on virtually every device and platform
• MKV - High-quality container for HD content with multiple audio tracks
• MOV - Apple QuickTime format recorded by iPhones and Macs
• AVI - Classic Windows format from the 1990s, still found in old archives
• WebM - Open format optimised for web streaming in browsers
• WMV - Windows Media Video, Microsoft proprietary format
• FLV - Flash video from the pre-2020 web era
• MPG / MPEG - DVD and broadcast standard compression
• MTS - AVCHD format from camcorders and Sony cameras
• 3GP - Legacy mobile format from 3G-era feature phones
• M4V - iTunes container (non-DRM files only)