What is __biz in a WeChat article link?

Open a WeChat article in a browser and the long form of its address looks like mp.weixin.qq.com/s?__biz=MzA5NTI3MjIwMA==&mid=2650412873&idx=1&sn=…. The first parameter, __biz, says which Official Account published it. Every article from that account carries the same value, and so does the account's profile page link (mp.weixin.qq.com/mp/profile_ext?action=home&__biz=…). That is why older scrapers and RSS tools ask for "the biz": it is the only account identifier that sits in plain sight in a web link.

What it looks like

• A Base64 string, almost always 16 characters ending in ==, such as MzA5NTI3MjIwMA==. In links copied out of HTML or other URLs it may appear percent-encoded, as MzA5NTI3MjIwMA%3D%3D.
• Decode it and you get a decimal number: MzA5NTI3MjIwMA== is 3095272200. The number has no other public use; keep the Base64 form, which is what every tool expects.
• It never appears in the short form of a link, mp.weixin.qq.com/s/ followed by a short code. Both forms open the same article; see mid, idx and sn for the rest of the long form.

How it differs from the other account IDs

ID	Looks like	Where you see it
__biz	MzA5NTI3MjIwMA==	Long article links, profile links
Original ID	gh_ + 12 hex characters	Account settings, page source, APIs
WeChat ID	a short handle such as brand_news	The account's profile in WeChat

None can be computed from another. You map them by looking them up; finding an account's IDs covers that from a name.

How the API relates to it

• Official Account article detail takes a short or long article link. It returns the full text and author.id, the account's original ID (gh_…). The url it returns is normally the long form, from which you can read __biz.
• Official Account article history takes the original ID or WeChat ID, not __biz. Each article's url in the list is a long link with __biz in it.
• Official Account search with view=full returns ext.biz for each account found, and url is the profile link built from it.

Task	Calls	Cost
One article link to full text and gh_ ID	1	$0.02
One account name to gh_ ID and biz	1	up to $0.58, $0.058 per account found
Latest 10 articles by gh_ ID	1	$0.02

Example: read __biz from any article link

import base64, os, requests
from urllib.parse import urlparse, parse_qs

r = requests.get("https://api.okdata.online/v1/wechat_mp/articles/get",
                 headers={"Authorization": f"Bearer {os.environ['OKDATA_API_KEY']}"},
                 params={"url": "https://mp.weixin.qq.com/s/k3Vq8ZtYwLr2PxN0aHd5Fg",
                         "fields": "id,url,title,author.id,author.name"},
                 timeout=60)
item = r.json()["data"]["item"]
biz = parse_qs(urlparse(item["url"]).query).get("__biz", [None])[0]
print(item["author"]["id"], biz, base64.b64decode(biz).decode() if biz else None)

Limits

• An account that went through WeChat's account migration ends up with new IDs; look it up again rather than trusting an old biz.
• Deleted articles return not_found, which is not charged.
• Getting the article text itself is covered in full text from a mp.weixin.qq.com link.