Basic Web-SDK event structure

Every event is sent to the server with a POST request to https://<server><pathPrefix>/<urlMark>/t4k.json with a JSON body. The page, sess, user, char, browser, and lib blocks are the same for all events, data depends on the event, and perf and scroll are not added to every event.

{
  "service": "track",
  "name": "page",
  "data": { "type": "content", "name": "Контакты" },
  "projectId": 1617632140,
  "uid": "6410748586712844288",
  "user": {
    "td": 0,
    "id": "42",
    "plan": "pro",
    "ga4ClientId": "2039255293.1537236640",
    "ymId": "1537242943246737376",
    "ts": 1757960000000,
    "tz": "Europe/Moscow",
    "tzo": 10800000
  },
  "page": {
    "title": "Rockstat",
    "path": "/contacts",
    "ref": "https://www.google.com/",
    "url": "https://example.com/contacts?utm_source=g",
    "query": { "utm_source": "g" },
    "domain": "example.com",
    "scheme": "https"
  },
  "sess": {
    "pageNum": 3,
    "eventNum": 17,
    "num": 2,
    "type": "campaign",
    "engine": "google",
    "refhost": "google.com",
    "marks": { "utm_source": "g" },
    "hasMarks": true,
    "marksHash": 123456,
    "start": 1757960000000
  },
  "char": { "ls": true, "ae": true, "pr": true, "sb": true, "ab": true, "wp": true },
  "browser": {
    "if1": 0, "if2": 0,
    "w": 1440, "h": 415, "tw": 1440, "th": 900, "aw": 1440, "ah": 836,
    "sopr": 2000, "soa": 0, "sot": "landscape-primary",
    "plt": "MacIntel", "prd": "Gecko",
    "uad": { "platform": "macOS", "platformVersion": "14.5.0", "mobile": false },
    "nc": { "effectiveType": "4g", "rtt": 50 },
    "ne": { "hc": 8, "dm": 8, "sq": 296630877388, "su": 12345 },
    "nb": { "a": 1, "ch": 1, "l": 100, "ct": 0, "dt": -1 }
  },
  "perf": { "cs": 0, "ce": 0, "scs": -1, "rqs": 211, "rss": 1549, "rse": 1560, "dl": 1581, "di": 1812, "dc": -1 },
  "scroll": { "dh": 1148, "ch": 326, "to": 479, "cs": 100, "ms": 100 },
  "lib": { "id": "web-sdk", "v": 5002001, "sv": 5002001, "st": 1757960000000 }
}

The query string carries dig — the body hash (cyrb53) — and td_trans — the transport used (b — beacon, f — fetch). More in the Transport section.

Message blocks#

Block	Content
name, data	The event name and its data. The list of automatic events and their data is in the Automatic events section
projectId	Project identifier from the configuration or the domain hash
uid	Visitor identifier. Stored in a cookie and localStorage
user	id and traits from identify; ga4ClientId and ymId from automatic synchronizations with GA4 and Yandex Metrica; ts, tz, tzo — the client's time and time zone; td — the clock offset from the server
page	url, path, query (the parsed query string, including UTM, gclid, yclid), ref, title, domain, scheme
sess	Session: number, start, counters, source type, marks. More in the Sessions section
char	Browser capabilities: ls localStorage, ae addEventListener, pr Promise, sb sendBeacon, ab atob, wp web push
browser	w/h — viewport, tw/th — screen, aw/ah — available area, sopr — devicePixelRatio × 1000, soa/sot — orientation, if1/if2 — iframe flags, plt/prd — platform and engine, uad — Client Hints, nc — network, ne — cores, memory, and storage quota, nb — battery
perf	Navigation Timing: cs connectStart, ce connectEnd, scs secureConnectionStart, rqs requestStart, rss/rse responseStart/End, dl domLoading, di domInteractive, dc domComplete. Only on page and page_loaded
scroll	dh — document height, ch — viewport height, to — offset from the top, cs — current scroll in percent, ms — maximum scroll on the page. On all events except session, page, page_loaded, user_params, rec_start, rec_batch
lib	id, v — the library version as the number major × 1e6 + minor × 1e3 + patch, sv — the snippet version, st — the library start time

Full event schema#

A dot in the keys marks a move to the next nesting level: page.title means { page: { title } }. The type {[string]:string} is a plain object with string keys and values. The JavaScript column describes what the browser sends; fields without it are added by the server.