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WeChat (Weixin) limitations

(Quick links: cache cleanup, audio. See also URL encoder for mobile chat.)

Many Chinese people now prefer to manage their contacts using a proprietary mobile messaging and social networking application called WeChat (微信)Wēixìn. This page notes some limits I found when sending documents etc on this platform.

Image and video limits

If pasting a scanned document into a WeChat conversation as an image, the size limit is 300KiB, after which the image is shown only as a blurred preview unless the recipient presses a small button they might not notice. So it's best to stay below 300KiB.

I have a separate page for technical information on creating narrow-column screenshots.

For inline videos:

The error "Unable to share this video due to unspported format" (e.g. if trying to post a short video to Moments) probably means you need to recode to h264.

By comparison, WhatsApp usually compresses inline images to around 250k (with no option to see full size) and limits video to 16MiB (as of 2017; best sent from the mobile application), and Telegram Messenger scales down to max 1280 pixels per dimension and sends the result as an 87%-quality JPEG (unless uploaded as a file) but has a much more generous video limit.

Audio recordings

MP3 files are sent as "files" no matter what, so the desktop application can be used ("drag and drop"); if using the mobile application, shared files (unlike videos) need to be added to "WeChat Favourites" before they can reliably be sent to a chat. Once in Favourites, the option to "forward" from the "Favourites" screen is unreliable; it seems better to go into the chat itself and press the + button, scroll to the Favourites option, and find the MP3 that way. Ensure it is uploaded before deleting from Favourites. After you delete it from Favourites, you will get the message "This file is no longer available" when you try to open it in the chat, but the other party should still be able to access it for a few days.

Cache bloat and hardware requirements

The Android version of WeChat can build up multiple gigabytes in a directory with a 32 hex-digit name under /sdcard/tencent/MicroMsg. These files are not the chat logs---they're just cache (and I haven't found an option to clear it; Android's built-in cache-clearing option does not affect this).

If a Chinese friend asks you to "fix" their WeChat on an older phone with internal storage measured in megabytes (such as the ChinaMobile-branded ZTE U809, which runs a version of Android 4.2 with only 177M of usable internal storage), beware this might no longer be possible because WeChat tends to insist on updating to its latest version, which now requires Android 5+ (partly because Tencent's own back-end servers now use HTTPS certificates not recognised by Android 4) and hundreds of megabytes of internal storage. Installing a very old smaller version of the APK will not work. The quickest solution could be to ask if they have a tablet or something to run it on instead: in one case I wasted 2½ hours trying 'hacks' only to find the person had already installed it on a tablet and didn't want it on their old phone that badly.

Length limits

If you rename your contacts, the new names are limited to 29 Unicode characters, and you are given a "too long" message if you try to set anything longer---so if your Chinese character skills are limited you can't write yourself too much of a reminder of how you met a person etc (unless you develop a terse shorthand code). Before the limit of 29 characters was implemented, there used to be a limit of 50 characters and the name would be truncated without warning; before that truncation was implemented, there used to be no practical limit. LINE's limit is only 20 characters, but at least there's a count (LINE also has other problems).

Comments on WeChat "official account" posts are limited to 600 characters---there is no warning until you try to post, and there is no character-count indicator, so if you run into problems there you may have to use a different editor with character count and paste in the result (unless you want to go back to 1960s/70s programming where you had to manually count out the number of characters you typed into a Hollerith constant!)

Chinese programmers might assume "one character" carries as much information as a Chinese character, so they may not realise how easy it is for English users to reach their limits. But the American developers of WhatsApp inexplicably limited group-chat titles to a mere 25 characters! (At least that limit is made obvious as you type.)

Disclaimer: The notes on this page are provided in the hope that they are useful, but they are not official instructions and may contain mistakes. Your use of them is at your own risk.

All material © Silas S. Brown unless otherwise stated.