Appendix B: GMC Custom Label Reference
Custom Label Specifications
Google Merchant Center provides five custom label attributes (custom_label_0 through custom_label_4) that merchants can use to segment products in Google Ads campaigns. These labels are not visible to shoppers and exist solely for campaign management purposes.
Technical Specifications
| Specification | Value |
|---|---|
| Number of labels | 5 (custom_label_0 through custom_label_4) |
| Maximum characters per label value | 100 |
| Maximum unique values per label | 1,000 |
| Total unique values across all labels | 5,000 |
| Case sensitivity | Not case-sensitive for matching |
| Visibility to shoppers | Not visible (internal use only) |
| Update frequency (Content API) | 2 updates per product per day maximum |
| Update frequency (Supplemental Feed) | Depends on feed fetch schedule (daily typical) |
Exceeding the 1,000 unique value limit: If a label has more than 1,000 unique values, additional values will not be processed for reporting or bidding purposes. Google does not surface an error; the excess values are silently ignored. AdPriority’s schema uses well under 100 unique values per label.
AdPriority Label Schema
Label Assignment
| Label | Purpose | Unique Values | Description |
|---|---|---|---|
custom_label_0 | Priority Score | 6 | The core AdPriority score (0-5) controlling budget allocation |
custom_label_1 | Season | 4 | Current season for the product |
custom_label_2 | Category Group | ~20 | Product category for reporting and sub-segmentation |
custom_label_3 | Product Status | 5 | Inventory and lifecycle status |
custom_label_4 | Brand Tier | 3 | Brand classification for bid adjustments |
Label 0: Priority Score
The primary label. Google Ads campaigns use this to create product groups with different budget allocations.
| Value | Meaning | Budget Behavior |
|---|---|---|
priority-5 | Push Hard | Maximum spend, aggressive bidding |
priority-4 | Strong | High spend, balanced approach |
priority-3 | Normal | Standard spend, conservative bidding |
priority-2 | Low | Minimal spend, strict ROAS targets |
priority-1 | Minimal | Very low spend, highest ROAS threshold only |
priority-0 | Exclude | Zero ad spend (excluded from campaigns) |
Label 1: Season
Indicates the current season context in which the priority was calculated. Useful for reporting (“How did winter products perform?”) and for creating season-specific asset groups.
| Value | Date Range (Default) |
|---|---|
winter | December 1 - February 28 |
spring | March 1 - May 31 |
summer | June 1 - August 31 |
fall | September 1 - November 30 |
Label 2: Category Group
Maps to the 20 AdPriority category groups. Enables granular reporting in Google Ads without creating separate campaigns per category.
| Value | Corresponding Category Group |
|---|---|
t-shirts | T-Shirts |
long-sleeve-tops | Long Sleeve Tops |
jeans-pants | Jeans & Pants |
sweatpants | Sweatpants |
shorts | Shorts |
swim-shorts | Swim Shorts |
hoodies-sweatshirts | Hoodies & Sweatshirts |
outerwear-heavy | Outerwear - Heavy |
outerwear-medium | Outerwear - Medium |
outerwear-light | Outerwear - Light |
headwear-caps | Headwear - Caps |
headwear-cold-weather | Headwear - Cold Weather |
headwear-summer | Headwear - Summer |
joggers | Joggers |
footwear-sandals | Footwear - Sandals |
footwear-shoes | Footwear - Shoes |
underwear-socks | Underwear & Socks |
accessories | Accessories |
women-apparel | Women - Apparel |
exclude | Exclude (non-advertisable) |
Label 3: Product Status
Reflects the product’s inventory and lifecycle state.
| Value | Criteria |
|---|---|
new-arrival | Product created within 14 days (configurable) |
in-stock | Has in-stock tag and positive inventory |
low-inventory | Has warning_inv_1 or warning_inv tag |
clearance | Has Sale tag |
dead-stock | Has DEAD50 or archived tag, or product status is archived |
Label 4: Brand Tier
Classifies products by brand recognition for bid adjustments.
| Value | Criteria |
|---|---|
name-brand | Has NAME BRAND tag, or vendor in recognized name brand list |
store-brand | Vendor is “Nexus Clothing” (or the store’s own brand) |
off-brand | Has OFF BRAND tag, or default for unrecognized vendors |
Current Nexus Usage (Verified 2026-02-10)
Audit of existing custom label usage across 124,060 products in the Nexus Clothing GMC account.
| Label | Current Value | Products Using | % of Catalog | Safe to Overwrite |
|---|---|---|---|---|
custom_label_0 | “Argonaut Nations - Converting” | 7 | 0.006% | Yes |
custom_label_1 | (empty) | 0 | 0% | Yes |
custom_label_2 | (empty) | 0 | 0% | Yes |
custom_label_3 | (empty) | 0 | 0% | Yes |
custom_label_4 | (empty) | 0 | 0% | Yes |
Conclusion: All five custom label slots are effectively available for AdPriority. The 7 products using custom_label_0 represent a negligible 0.006% of the catalog. These are legacy values from a previous experiment and can be safely overwritten.
Unique Value Budget
AdPriority’s label schema uses far fewer unique values than the 1,000-per-label limit:
| Label | Unique Values Used | Limit | Utilization |
|---|---|---|---|
custom_label_0 | 6 | 1,000 | 0.6% |
custom_label_1 | 4 | 1,000 | 0.4% |
custom_label_2 | 20 | 1,000 | 2.0% |
custom_label_3 | 5 | 1,000 | 0.5% |
custom_label_4 | 3 | 1,000 | 0.3% |
| Total | 38 | 5,000 | 0.8% |
This leaves ample room for merchants to add custom values for their own use cases without approaching the limit. Even a store with highly granular category groups (100+ types) would remain well under the threshold.
Using Labels in Google Ads
PMAX Campaign Structure
Custom labels enable segmentation within Performance Max campaigns via listing group filters.
PMAX CAMPAIGNS USING CUSTOM LABELS
===================================
Campaign: "PMAX - Push Hard"
Listing Group Filter:
custom_label_0 = "priority-5"
Budget: $50/day
Target ROAS: 3.0x
Campaign: "PMAX - Strong"
Listing Group Filter:
custom_label_0 = "priority-4"
Budget: $35/day
Target ROAS: 4.0x
Campaign: "PMAX - Standard"
Listing Group Filter:
custom_label_0 = "priority-3"
Budget: $20/day
Target ROAS: 5.0x
Campaign: "PMAX - Low Priority"
Listing Group Filter:
custom_label_0 IN ("priority-1", "priority-2")
Budget: $10/day
Target ROAS: 6.0x
Products with "priority-0": Not included in any campaign
Reporting Dimensions
In Google Ads reports, custom labels appear as reportable dimensions. Merchants can analyze:
- Spend, revenue, and ROAS by priority level (
custom_label_0) - Performance by season (
custom_label_1) - Category-level metrics (
custom_label_2) - New arrival vs. established product performance (
custom_label_3) - Brand tier performance (
custom_label_4)