Ga4 Data API Query

GA4 Data API v1 — runReport

The Data API v1 is the canonical read path for GA4. One endpoint (runReport) covers most use cases. Two paths matter for picking the right query: dimensions describe rows (date, page, source), metrics describe values (sessions, users, events). Not every combination is valid — see "Compatibility" below.

Prerequisite: auth working (see ga4-auth-setup).

The minimum viable query

from google.analytics.data_v1beta import BetaAnalyticsDataClient
from google.analytics.data_v1beta.types import (
    RunReportRequest, DateRange, Metric, Dimension,
)

client = BetaAnalyticsDataClient()

req = RunReportRequest(
    property="properties/123456789",     # YOUR property ID (digits only)
    date_ranges=[
        DateRange(start_date="30daysAgo", end_date="today"),
    ],
    metrics=[Metric(name="activeUsers")],
    dimensions=[Dimension(name="date")],
)
resp = client.run_report(req)

for row in resp.rows:
    date = row.dimension_values[0].value     # YYYYMMDD string
    users = row.metric_values[0].value       # numeric string
    print(f"{date}: {users}")

That's the full skeleton. Everything below extends this shape.

The 12 metrics worth knowing

bounceRate and averageSessionDuration are ratios — don't SUM them across rows; they're already aggregated within each row's group.

The 12 dimensions worth knowing

Compatibility — not every (dim, metric) combo is valid

GA4 enforces a compatibility matrix at the API level. If you ask for sessions + customEvent:purchaseId together you may get an empty result or a 400 INVALID_ARGUMENT. Two rules cover ~90% of cases:

1. User-scoped vs session-scoped vs event-scoped dimensions don't always mix with each other's metrics. Stick to dimensions in the same scope as your headline metric where possible.
2. High-cardinality custom dimensions can trigger sampling. GA4 will silently sample if a single query touches more than the property's data-quota threshold; the response includes metadata.dataLossFromOtherRow=true. Check it.

If you're unsure, query the compatibility metadata endpoint:

from google.analytics.data_v1beta.types import CheckCompatibilityRequest
compat = client.check_compatibility(CheckCompatibilityRequest(
    property="properties/123456789",
    dimensions=[Dimension(name="pagePath"), Dimension(name="sessionSource")],
    metrics=[Metric(name="screenPageViews"), Metric(name="sessions")],
))
print(compat)

Filters

Filters are nested expressions. The common case: filter rows by a dimension value.

from google.analytics.data_v1beta.types import (
    FilterExpression, Filter, FilterExpressionList,
)

# Just pages under /docs/
docs_only = FilterExpression(
    filter=Filter(
        field_name="pagePath",
        string_filter=Filter.StringFilter(
            match_type=Filter.StringFilter.MatchType.BEGINS_WITH,
            value="/docs/",
            case_sensitive=False,
        ),
    ),
)

# AND combine: organic search AND not from referrer "spam.com"
combined = FilterExpression(
    and_group=FilterExpressionList(expressions=[
        FilterExpression(filter=Filter(
            field_name="sessionMedium",
            string_filter=Filter.StringFilter(
                match_type=Filter.StringFilter.MatchType.EXACT,
                value="organic",
            ),
        )),
        FilterExpression(not_expression=FilterExpression(filter=Filter(
            field_name="sessionSource",
            string_filter=Filter.StringFilter(
                match_type=Filter.StringFilter.MatchType.EXACT,
                value="spam.com",
            ),
        ))),
    ]),
)

req = RunReportRequest(
    property="properties/123456789",
    date_ranges=[DateRange(start_date="30daysAgo", end_date="today")],
    metrics=[Metric(name="sessions")],
    dimensions=[Dimension(name="pagePath")],
    dimension_filter=docs_only,
)

Use metric_filter for filtering by metric (e.g. only rows where sessions > 100). Same shape.

Date ranges

GA4 has 48-hour data freshness — today's numbers fluctuate; yesterday's settle ~24h after midnight in the property's timezone; numbers older than 48h are stable. Don't draw conclusions from "today" alone.

Multiple date_ranges in one request gives you a comparison report:

DateRange(start_date="30daysAgo", end_date="yesterday", name="current"),
DateRange(start_date="60daysAgo", end_date="31daysAgo", name="prior"),

The response will have dateRange as an extra dimension on each row.

Pagination

req = RunReportRequest(
    # ... as above
    limit=10_000,    # max 250_000 per request
    offset=0,
)
resp = client.run_report(req)
# resp.row_count is the TOTAL matching rows; resp.rows is the current page
while resp.row_count > req.offset + len(resp.rows):
    req.offset += len(resp.rows)
    resp = client.run_report(req)
    # process resp.rows

For result sets over ~1M rows, use ga4-bigquery-export instead.

Sampling — always check

resp = client.run_report(req)
if resp.metadata.data_loss_from_other_row:
    print("WARNING: data was sampled. Tighten date range, drop high-cardinality dimensions, or use BigQuery export for unsampled data.")

If sampled, results are statistically valid but not exact. For exact counts, BigQuery export is the only path.

Common errors

Related skills

• ga4-auth-setup — prerequisite
• ga4-realtime-api — for "right now" data instead of runReport's ~24h lag
• ga4-common-reports — copy-paste recipes for the canonical 6-7 reports
• ga4-bigquery-export — when you've outgrown the Data API

Source: jeremylongshore/claude-code-plugins-plus-skills → plugins/saas-packs/ga4-pack/skills/ga4-data-api-query/SKILL.md