What Is an API Feed? How Product Data Feeds Work

An API feed is a connection through which one system requests current product records from another, or pushes changes to it, one record at a time instead of in a scheduled file.

The gap it closes is time. I worked out that a daily file fetch leaves a price change unseen by Google for 12 hours on average, using Google’s own fetch schedules and assuming changes land evenly through the day.

An API feed shortens that wait, but only if you check what Google did with the update.

What is an API feed?

An API feed is a product data feed delivered through an application programming interface (API): software asks for specific records, or sends them, through agreed endpoints.

If a file feed is a printed price list, an API feed is a phone line to the stockroom.

The National Institute of Standards and Technology’s API definition calls an API a system access point with well-defined syntax that application programs can use. In practice, both systems agree on four things:

The record itself holds structured fields such as SKU, price, availability and stock.

Can an API feed change data, or only read it?

An API feed can do either, depending on the permissions it grants. An advertising platform might only read your products, while a connected app might also write an update back to the source.

Permission to read never implies permission to write, so check both before you connect anything.

Data feed vs API feed: what’s the difference?

A data feed (file feed) delivers a full snapshot on a schedule; an API feed moves individual records when they are requested or changed.

The choice decides how fresh your prices are and how much engineering you take on.

How stale can a file feed get?

A file feed can be up to one full interval out of date, because a change made just after a fetch waits for the next one.

Google Merchant Center fetches a file feed daily, weekly or monthly at a set hour, as Google’s scheduled data-feed documentation lists.

Show the dataHide the data

Hours before a price change reaches Google, by update method

Hours, by update method	Average wait	Worst case
Weekly file fetch	84	168
Daily file fetch	12	24
API poll every hour	1	1

A monthly fetch can be up to a month behind. An API poll or push removes most of that wait, but your store still has to detect the change, the connector has to send it and Google has to process it.

A neglected API job leaves prices as stale as a neglected export.

Format is a separate decision from delivery. CSV is easy to inspect in a spreadsheet, while JSON handles nested structures such as variants; Scrappey’s guide helps you compare CSV and JSON formats before you settle on one.

How does an API feed work?

An API feed works as a short exchange between a client, the software asking, and a server, the software answering. The client is usually a connector, not a person in a browser.

Many product APIs, including Google’s Merchant API, follow REST, the architectural style that Roy Fielding introduced in his 2000 doctoral dissertation at the University of California, Irvine, as this IEEE Computer article on REST describes.

REST identifies each resource by a URL and keeps requests stateless: every request carries everything needed to process it.

REST doesn’t define what a record means. The API’s documentation has to settle identifiers, units, currency, timestamps and which kind of message each call sends:

What keeps an API feed reliable?

Four controls keep an API feed from failing quietly or creating duplicates:

Caching needs a deliberate setting per field, because a cached price is a stale price:

Choose the simplest method that meets your freshness and recovery needs. A well-run file feed beats a neglected API.

Why doesn’t a successful API call mean a live product?

A successful API call means Google stored what you sent, not that the product can appear in ads.

Google’s Merchant API product overview separates ProductInput, the raw data you submit, from Product, the read-only result after feed rules, supplemental data and validation, including its final status and issues.

Say a retailer sends Google Shopping a lower jacket price through the Merchant API, which replaced Content API for Shopping in 2026.

The request returns 200, the merchandiser sees the new price in the store, and the marketer assumes the ad is updated.

The Merchant API writes through insert, patch and delete on ProductInput, and reads through get and list on Product.

A connector can patch one attribute rather than resend the whole product set, but it should always read the processed product back. Our Merchant API guide covers authentication and the daily call quota that read-back uses.

Polling or webhooks: which keeps a feed fresher?

Webhooks keep a feed fresher because the source announces each change, while polling only finds changes at the next check. Polling is simpler to run and recover:

Neither removes reconciliation. A missed webhook leaves a gap only a scheduled comparison of source and destination will find.

Where do API feeds go wrong?

API feed failures usually show up as a mismatch between your store and Google Shopping. Diagnose the symptom before changing the architecture:

Track freshness lag where the record becomes usable, not when your connector sent it, along with rejected records, duplicates and recovery time.

Give every alert a named owner; for rejections, our list of Merchant Center errors gives the fix for each.

A correct feed lets Google show the right product. It doesn’t tell you which products deserve more priority.

At Product Metrics, we read your Google Ads and Merchant Center data and write only the labels you approve: Product Segmentation sends each product’s segment to Merchant Center as a custom label through a supplemental feed. We never change your prices.

Which product fields should an API feed share?

An API feed should share only the fields and operations the recipient needs, a principle called least privilege. A product record often sits next to cost price, margin, exact stock and unpublished prices that Google never needs.

Akamai’s 2026 API Security Study, a survey of 1,840 security professionals published in April 2026, found that 87% of organisations had an API-related security incident in the previous year, and fewer than one in four knew which of their APIs return sensitive data.

Set field-level permissions where the API supports them, rotate tokens and keep test and production apart. Audit logs should record who read or changed which record, without storing the sensitive payloads themselves.

How do you protect the feed itself?

Protect the feed by authenticating every webhook, rejecting replayed messages and rate-limiting without blocking legitimate recovery traffic. Akamai’s 2026 application and API security report counted 258 daily API attacks per enterprise in 2025, up 113% from 121 in 2024.

Show the dataHide the data

Average daily API attacks per enterprise

Year	Daily API attacks
2024	121
2025	258

Then ask each feed provider five questions:

A provider that can’t answer the last question can’t prove its feed is accurate. Our guide to Merchant Center feed rules shows where source values can change on the way in.

Should your store use an API feed?

Use an API feed when prices or stock change between scheduled fetches, or when a recipient needs single-record updates or write-back. If a daily snapshot is fresh enough, a file feed is easier to run.

Two signals in the right-hand column usually settle it. For the file route, our guide to Google product feeds covers ID mapping and fetch schedules.

How do you test an API feed before trusting it?

Test an API feed by tracing a handful of SKUs from source value to processed destination product.

Map each source field to its destination and document transformations such as availability values, currency and variant IDs, so developers and merchandisers check the same results.

Set a freshness target in minutes or hours that matches the cost of a stale price, then run four test records through it:

Setting up Product Metrics means connecting Google Ads and Merchant Center, choosing ROAS or POAS and adding the supplemental feed once; it doesn’t replace these checks on the records underneath.

Final thoughts

The green “connected” light is the least useful signal an API feed gives you. What counts is the processed product: the right price, an approved status, within a time you set.

Approve an integration when your team can show those three on real SKUs, including the broken ones.

When the feed spans a commerce platform, a warehouse system and a supplier network, Continuum Solutions’ system integration support for enterprise teams is one way to settle who owns each connection.

If you run a dropshipping store, supplier choice comes before feed design, because the supplier’s own stock data is what your feed passes on. A guide to find suppliers for Shopify jewelry dropshipping covers the sourcing side.