Publishing one video in several places means checking its duration and size as well as its shape and file format. I built FlowWorth to read those properties from a selected file and show them alongside the rules for its destination. I chose a free, functional tool, with the verdict and the source behind it on the same screen.
The current page compares YouTube Shorts, Instagram Reels, TikTok Non-Spark In-Feed Ads, LinkedIn organic video posts, Pinterest standard-width video and X standard video posts. An ordinary post and an advertisement can follow different rules even on the same platform, so I labelled the publishing surface rather than treating a platform name as a complete specification. Open FlowWorth
The right shape can still have too few pixels
A vertical video is not a complete description of a file. A 360-by-640-pixel video has the same 9:16 aspect ratio as a 1080-by-1920 video, but fewer pixels form the picture. I kept aspect ratio and resolution as separate checks, alongside duration and file size.
For example, selecting a three-second synthetic MP4 measuring 360 × 640 produces a duration of 0:03, a ratio of 9:16 and a resolution of 360 × 640. In the current Instagram comparison, duration and ratio receive PASS, while resolution receives FIX. A pass means that one property matches the rule being applied; a fix identifies a condition to change. Neither is a promise that the platform will accept the upload.
Unresolved conditions remain VERIFY. If a cited source does not give a universal size limit, or the browser cannot read the information needed for a check, the tool leaves that uncertainty visible instead of supplying a guessed number. Passing one check should not be mistaken for clearance to publish the whole file.
What the browser reads—and what it leaves open
On file selection, the browser's File API supplies the name and size in bytes. If the browser can read the video, it also supplies the duration and pixel dimensions. The File API lets a webpage access a file the user has chosen. I set up the checker to use a temporary reference to that file inside the browser, rather than send the video to a server for inspection.
The implementation creates that reference with URL.createObjectURL, reads the basic information through a video element, and releases the reference with URL.revokeObjectURL. It also releases the reference when reading fails. In that case, duration, aspect ratio and resolution appear as unreadable with VERIFY; an unreadable duration is not displayed as a zero-second video.
A filename ending in .mp4 does not establish how the video inside it was encoded. MP4 is a container that holds media such as video and audio, while a codec compresses and decodes that media. The current format check uses the filename extension; it does not inspect the internal codec. Codec and frame rate, which browsers do not expose consistently for every local file, remain checks to make in an editor.
The file-inspection component contains no request to transmit the selected video. This does not establish how every browser behaves or verify all the site's communications. I also explained the file-handling approach and the information it cannot read on the Method page.
Keeping a route back to the rule
An accurate duration reading can still produce bad guidance if it is compared with an outdated limit. I put official sources and last-reviewed dates on the platform cards, with links to a fuller explanation of each rule. The Instagram brief, for example, distinguishes the size and duration conditions from file-format and file-size claims that the cited source does not establish. Instagram sources and scope
A review date records when a rule was examined. It does not mean that the platform has kept the rule unchanged since then, so the current source still needs checking when using a result. The earlier work also included a source brief and a weekly update watch to respond to those changes.
FlowWorth brought together the interaction I wanted to build: read a file, compare different publishing conditions and keep the supporting evidence within reach. Copyright, account restrictions and the platform's final acceptance remain outside its checks. The public tool and its basic file checks can be inspected, but I have not measured how many failed uploads it prevents or how much time it saves users.