I just read SomeOtherStranger's blog post "2025/07/09 - Why the Web Still Needs Flash” and I just wanted to chime in with my nerd knowledge on video codecs and containers.

NOTE, take this with a grain of salt, I'm mostly making educated guesses here!

Grain of salt taken.

By contrast, most video formats store the data for each frame individually. I'm guessing that compression may allow it to save on data cost if thre [sic] isn't much change between one frame and another...

Regarding the first sentence, this is only partially true. A codec designed for and used primarily by video editors, such as DNxHR, does save each and every frame individually. The reason for this is to make scrubbing through video faster (it's more technical than this, but the tl;dr is that it's easier for the CPU to render frames). However, videos using these types of codecs aren't seen/used online due to their massive file sizes. What is used is the H.264 codec (huh?) in a MP4 container (oh!), which uses interframe compression to only save changes between frames, and not each frame individually, therefore saving a lot of space. The VP9 codec (developed by Google), typically used in a WEBM container, performs similarly.

...but that doesn't really help much if there's a lot of change each frame.

You'd be surprised. H.264 also makes use of motion estimation, which saves even more space by simply saying "Move these specific pixels to the left” instead of needing to save a whole new frame or even just the changes between frames. A good explanation can be found on the /r/VideoEditing wiki.

The MP4 video is 1388 x 1080 (about HD) at 30 FPS, 2 minutes 49 seconds, and has a bitrate of 4.65 Mbits per second. It's [sic] filesize is 94.3 MB. The video is largely black lineart on a white background, with music and sound effects, and various action shots. It's hand-drawn frame-by-frame animation.

Not saying that it's impossible for an MP4 to get to that size, but you can get a video file significantly smaller than ~94MB by adjusting some settings using Handbrake or something. For example, using H.265 instead of H.264, saving fewer i-frames, etc. But I agree with what is said next...

Contrast that with the SWF, which is only 6 MB. 6 MB for the same animation, music and sound effects, while being able to be scaled to any size without losing quality.

...Which is that vector graphics obviously outperforms raster graphics. Hell, my logo and branding are SVGs I made in Inkscape! But vector bears the significant disadvantage of only being useable in very specific applications. Most people like to draw digitally, or take pictures of things, or shoot videos of the real world, which simply cannot be vectorized. I think it is part of the reason why Flash fell out of favor: people wanted to make and share things that were inappropriate for use with Flash.

Point is, there's still a valid use for Flash on the web and because of that it's a shame that there wasn't a proper replacement for it. But hey, at least we can still use Flash.

Agreed. Although Flash served a niche purpose, dropping it without a suitable replacement is unfair. Shout out Flashpoint Archive!