What Sources Are Available in Google Analytics? 2026

If you've been digging through Google Analytics 4 acquisition reports and seen the "Source" dimension — and wondered exactly which sources GA4 recognizes out of the box, how they get classified, and what happens to sources GA4 doesn't know about — you're not alone. Sources available in Google Analytics 4 are not a fixed list — GA4 captures any source string a session arrives with, but it recognizes ~60 well-known sources (google, bing, facebook, instagram, youtube, linkedin, twitter, tiktok, baidu, yandex, naver, duckduckgo, ecosia, brave, yahoo, ask, aol, mail.ru, and others) and automatically maps them to default channel groupings like Organic Search, Paid Search, Organic Social, and Email; anything outside that list — including any string you pass through `utm_source` — also becomes a Source, but lands in (other) or Referral unless you explicitly classify it. This guide explains exactly what a Source is in GA4, the sources GA4 recognizes natively, where to find them, how custom sources work, and how Source interacts with Medium and Channel Grouping in 2026.

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What Is a Source in Google Analytics? The Direct Answer

In simple terms, a Source in GA4 is the specific origin of a session — typically a website domain, a search engine name, or a campaign source value passed via UTM. It's paired with Medium (the *type* of source — like organic, cpc, email, referral) to form the classic `source / medium` dimension.

Examples:

`google / organic` — a free click from Google Search
`google / cpc` — a paid click from Google Ads
`facebook.com / referral` — a click from a link on Facebook
`newsletter_may / email` — a click from a UTM-tagged email
`(direct) / (none)` — a session with no detectable source

GA4 doesn't ship with a hard "allowed sources" list. Any string sent via `utm_source` becomes a Source. But GA4 *does* maintain an internal list of ~60 well-known sources (search engines, social platforms, and big email providers) that it auto-classifies into channel groups without UTMs.

The Default Sources GA4 Recognizes Out of the Box

These are the sources GA4 automatically classifies — no UTMs required.

Search Engine Sources (auto-classified as Organic Search)

GA4's built-in search engine list includes:

google — Google Search
bing — Microsoft Bing
yahoo — Yahoo Search
duckduckgo — DuckDuckGo
baidu — Baidu (China)
yandex — Yandex (Russia)
naver — Naver (Korea)
daum — Daum (Korea)
ecosia — Ecosia
ask — Ask.com
aol — AOL Search
brave — Brave Search
seznam — Seznam (Czech Republic)
kvasir — Kvasir (Norway)
rambler — Rambler (Russia)
lycos — Lycos
so.com — 360 Search (China)
sogou — Sogou (China)

When a session arrives from one of these domains with no UTMs, GA4 reads the referrer, identifies the search engine, and tags the session as `<source> / organic`.

GA4's built-in social platform list includes:

facebook / facebook.com / m.facebook.com / l.facebook.com
instagram / instagram.com / l.instagram.com
twitter / twitter.com / t.co / x.com
linkedin / linkedin.com / lnkd.in
youtube / youtube.com / m.youtube.com
tiktok / tiktok.com
pinterest / pinterest.com
reddit / reddit.com / out.reddit.com
snapchat / snapchat.com
whatsapp / whatsapp.com
telegram / t.me
quora / quora.com
medium / medium.com

Click-throughs from these platforms land as `<source> / referral`, then get reclassified to Organic Social by the default channel grouping rules.

Video Sources (auto-classified as Organic Video)

youtube.com
vimeo.com
dailymotion.com
twitch.tv
tiktok.com (overlaps with Organic Social — GA4's logic picks Video when watch-page referrers are detected)

Shopping Sources (auto-classified as Organic Shopping)

amazon.com / amazon.co.uk / etc.
ebay.com
etsy.com
walmart.com
alibaba.com

Email Sources (auto-classified as Email)

GA4 doesn't auto-detect email — it relies on `utm_medium=email`. Common source values you'll see when sessions are properly tagged:

mailchimp
klaviyo
hubspot
brevo
convertkit
<your_newsletter_name>

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Sources From UTM Parameters

The mechanism behind every non-Google source.

When you build a tagged link like:

`https://yoursite.com/?utm_source=newsletter&utm_medium=email&utm_campaign=may_promo`

GA4 reads `utm_source=newsletter` and stores `newsletter` as the Source. The medium (`email`) then triggers the Email default channel grouping rule.

You can pass *any* string as a source — `partner_xyz`, `qr_code_print_ad`, `affiliate_johndoe`, anything. GA4 stores it verbatim. Just be consistent: `Newsletter` and `newsletter` are treated as different sources.

Sources From Referrers

When a session arrives with no UTMs but a detectable referrer, GA4:

Reads the referrer URL
Extracts the domain
Checks it against the built-in source list (search engines, social platforms, video, shopping)
If it matches: applies the right channel grouping automatically
If not: stores the domain as the source and classifies as Referral

So a click from `medium.com/somearticle` arrives as `medium.com / referral`, then gets reclassified as Organic Social because Medium is on the social list. A click from a random blog like `johndoe.com/post` arrives as `johndoe.com / referral` and stays in the Referral channel.

Where to Find Source Reports in GA4

The specific places.

Acquisition → Traffic Acquisition

The main report. Add Session source or Session source / medium as a secondary dimension. This shows your top traffic sources by sessions, engaged sessions, and conversions.

Acquisition → User Acquisition

Same as Traffic Acquisition but attributed to first-touch source for each user.

Explorations

Build custom reports that combine Source with other dimensions (landing page, country, device, conversion event) for deeper analysis.

Reports → Engagement → Pages and Screens

Add Source as a secondary dimension to see which sources drive traffic to which pages.

Real-Time

Watch live sessions land and confirm which Sources they're arriving with — useful for verifying UTM tagging on new campaigns.

A quick disambiguation.

Source vs Medium

Source: where the traffic came from (google, facebook, newsletter_may)
Medium: the *type* of traffic (organic, cpc, email, referral, social)
Always paired in reports as `source / medium`

Source vs Channel Group

Source: granular — one specific origin
Channel Group: aggregated bucket of similar sources (e.g., Organic Search rolls up google + bing + duckduckgo + others into one channel)

Source vs Referrer

Source: GA4's dimension value (sometimes the same as the referrer domain, sometimes overridden by UTMs)
Referrer: the literal HTTP referrer header from the browser

Source vs Campaign

Source: the platform or origin
Campaign: the specific marketing campaign (typically passed via `utm_campaign`)

Source vs Default Channel Group

The Default Channel Group is GA4's mapping rule that translates Source + Medium combinations into named channels (Organic Search, Paid Search, etc.). The Source itself is just the raw value.

How to Read Source Reports

Practical patterns.

1. Always Pair Source With Medium

`source / medium` together tells you a complete story. Just "google" is ambiguous (organic? paid?). `google / organic` vs `google / cpc` is a real answer.

2. Compare Source Performance Across Conversion Rates

Sort by conversion rate, not just sessions. A small source converting at 8% is more interesting than a big source converting at 0.4%.

3. Watch for "(other)" and "(not set)"

If a chunk of sessions show up as `(other)` or `(not set)`, GA4 couldn't classify them. That usually means broken UTM tagging or a referrer GA4 doesn't recognize.

4. Look at New vs Returning by Source

Add new vs returning user as a secondary dimension. Some sources (paid, social) lean new-visitor heavy. Some (email, direct) lean returning.

5. Compare Engagement Quality by Source

Engagement rate, engaged sessions per user, and event count per session vary wildly by source. Use these to evaluate source quality, not just session volume.

6. Track AI Search Sources Separately

In 2026, AI search engines (chatgpt.com, perplexity.ai, claude.ai, gemini.google.com, copilot.microsoft.com) are increasingly major sources. Most show up as Referral by default in GA4, since they're not in the built-in search engine list yet. Create a custom channel group to bucket them.

Custom Sources You'll Want to Track

Common ones that need explicit UTMs.

AI Search Engines

GA4 doesn't yet auto-classify AI search engines as search sources. Tag your share/recommend links from AI-friendly content with `utm_source=chatgpt&utm_medium=ai_search` (or similar) and create a custom channel grouping rule.

Podcast Show Notes

`utm_source=podcast_name&utm_medium=podcast`. Otherwise these show up as Direct since podcast players don't pass referrers.

QR Codes

`utm_source=qr_print&utm_medium=offline`. Otherwise: Direct.

Mobile App Notifications

`utm_source=app_push&utm_medium=push`. App browsers strip referrers.

Affiliate Networks

`utm_source=<affiliate_id>&utm_medium=affiliate`. Don't leave them lumped in with Referral.

SMS Campaigns

`utm_source=sms_blast&utm_medium=sms`. SMS clicks don't pass referrers.

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Limitations of GA4 Source Data

A few honest caveats.

The "available" list isn't published. Google maintains the built-in source list internally and updates it without notice. Treat this guide as accurate as of 2026 but expect minor changes.

AI search engines aren't auto-classified yet. ChatGPT, Claude, Perplexity, and Gemini referrals show as Referral, not Organic Search, until Google updates the default channel grouping.

Same source different cases get split. `Facebook` and `facebook` are different Source values in reports. Always lowercase your UTM sources.

Self-referrals can pollute Sources. If GA4 picks up a referrer from your own subdomain, it'll show as a referral. Configure the Internal Domains list in Admin → Data Streams → Tagging settings.

Source attribution depends on consent. Users who decline analytics consent contribute modeled session counts but no source detail.

Source doesn't carry across the funnel cleanly. GA4 uses Session-scoped vs User-scoped attribution. Choose the right one for your analysis.

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How to Add a Source GA4 Doesn't Recognize

Three steps.

1. Tag Your Inbound Links With UTMs

Use `utm_source=<your_source>&utm_medium=<appropriate_medium>` on every external link you control.

2. Update the Default Channel Group (Optional)

In Admin → Data Display → Channel groups, customize the rules to route your new source into the right channel bucket. For example, route `utm_source=chatgpt` into a custom "AI Search" channel.

3. Create a Custom Channel Group

If you want to keep the default GA4 channel group intact but also have your own view, create a custom channel group. Useful for comparing scenarios without rewriting defaults.

Final Thoughts

Sources in Google Analytics aren't a fixed list — GA4 captures any source string a session arrives with, but it recognizes about 60 well-known sources out of the box (Google, Bing, Facebook, Instagram, YouTube, LinkedIn, TikTok, Baidu, Yandex, Naver, DuckDuckGo, Ecosia, Brave, Yahoo, and others) and automatically maps them to the right default channel groupings. Anything outside that list — including any string you pass through `utm_source` — also becomes a Source, but it lands in Referral or "(other)" unless you classify it explicitly. To get the most out of Source data, always pair Source with Medium, watch for "(other)" and "(not set)" segments that signal tagging gaps, and create custom channel groupings for sources that matter to your business (especially AI search engines in 2026).

Beyond the standard Sources GA4 ships with, the bigger 2026 question for marketing teams is whether the channels driving your real buyer intent are visible in your reports at all. Increasingly, that intent originates in AI search engines like ChatGPT, Claude, Perplexity, and Gemini — channels that GA4 still files under Referral or Direct. Run a free audit to see exactly where your site performs across Google AND every major AI search platform — and which fixes will move the needle fastest this quarter.

SEO STUFFv2.1

What Sources Are Available in Google Analytics? (2026 Guide)