What Is Inline Inspection?
Inline inspection — also known as During Production Inspection (DUPRO) — is a quality control check carried out while manufacturing is still in progress. Rather than waiting until every unit has been produced, an inspector visits the factory when roughly 10% to 60% of the order is complete. The goal is simple: identify workmanship problems, material defects, and specification deviations early enough to correct them before the full batch is finished.
During an inline inspection, the inspector examines completed units using the same defect classification system used in any pre-shipment inspection — critical, major, and minor defects. However, because the order is not yet complete, the inspection is typically advisory rather than a formal pass/fail decision. The inspector provides a detailed report highlighting issues found, and the factory has the opportunity to implement corrective actions on the remaining production.
Inline inspection is particularly valuable for products with multiple assembly stages, such as electronics, furniture, or garments. By checking quality at key production milestones, buyers can prevent an entire lot from being produced with the same recurring defect — a situation that is far more expensive to fix after the fact.
Key point: Inline inspection is preventive. It reduces the risk of mass defects by catching issues when only a fraction of the order is complete, saving time and rework costs.
What is the difference between inline and final inspection?
The core difference comes down to timing and purpose. Inline inspection happens during production; final inspection (also called pre-shipment inspection or PSI) happens after production is 100% complete and at least 80% of the order is packed for shipment.
| Criteria | Inline Inspection (DUPRO) | Final Inspection (PSI) |
|---|---|---|
| Timing | 10%–60% of production complete | 100% complete, 80%+ packed |
| Purpose | Identify and correct issues early | Pass/fail decision on the finished lot |
| Sampling basis | Finished units available at the time | Full lot, per Acceptable Quality Level tables |
| Outcome | Advisory report with corrective actions | Formal accept or reject decision |
| Corrective window | Factory can fix remaining production | Limited to rework or re-inspection |
In practice, the two inspections complement each other. Inline inspection reduces the likelihood of a failed final inspection. Relying solely on a final inspection means defects are only discovered when it is too late to fix them without significant cost and delays.
What is meant by final inspection?
Final inspection, often referred to as pre-shipment inspection (PSI), is the last quality gate before goods leave the factory. It is conducted once 100% of the order has been manufactured and at least 80% is export-packed. The inspector draws a random sample from the finished lot based on Acceptable Quality Level sampling tables (ISO 2859-1) and checks each sampled unit against the buyer's specifications.
Unlike inline inspection, the final inspection results in a clear pass or fail verdict. If the number of defects found in the sample exceeds the accept number for the chosen AQL, the entire lot is rejected. The buyer then decides whether to accept the goods as-is, request rework and re-inspection, or cancel the order. You can use an AQL Calculator to determine the exact sample size and accept/reject criteria for your lot.
When should you use inline inspection?
Inline inspection is not required for every order, but it becomes essential in certain situations. Consider scheduling one when:
- Working with a new supplier — You have no quality track record and need early visibility into their workmanship and processes.
- Large or high-value orders — The financial risk of a failed final inspection is significant. Catching defects at 20% completion is far cheaper than reworking 100% of the lot.
- Complex products with multiple assembly stages — Electronics, furniture, and machinery where errors in early stages get buried under subsequent assembly.
- Previous quality failures — If the same factory failed a recent final inspection, an inline check ensures corrective actions have actually been implemented.
- Tight delivery deadlines — When there is no room for rework or re-production, early detection is the only way to stay on schedule.
- Custom or first-time products — New designs carry higher risk of misinterpretation by the factory. An inline inspection confirms the product matches the approved sample.
Rule of thumb: If the cost of a failed shipment exceeds the cost of an extra inspection visit, schedule an inline inspection. For most importers, this threshold is reached on any order above $5,000.
How to conduct an effective inline inspection?
A well-executed inline inspection follows a structured process. Here is how to get the most value from every visit:
1. Time the visit correctly
Schedule the inspection when 20% to 40% of the order is complete. Too early and there are not enough finished units to evaluate. Too late and there is not enough remaining production to correct any issues found.
2. Prepare a clear inspection checklist
Provide the inspector with detailed specifications, approved samples, packaging requirements, and a list of defects to watch for. The checklist should cover dimensions, materials, colours, function, labelling, and any regulatory requirements.
3. Inspect both finished and in-process units
Check completed units for workmanship, and walk the production line to observe assembly methods, raw material handling, and work-in-progress. Production line observations often reveal systemic issues that random sampling alone would miss.
4. Verify materials and components
Confirm that the factory is using the correct raw materials, components, and packaging materials as specified. Material substitution — whether intentional or accidental — is one of the most common problems caught during inline inspections.
5. Document and communicate findings immediately
The inspection report should be issued within 24 hours, with photographs of every defect found. Share it directly with the factory management and your sourcing team so corrective actions can begin without delay.
6. Follow up
For serious issues, schedule a second inline inspection or bring forward the final pre-shipment inspection to verify that corrective actions have been effective.
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Book Inspection →Frequently Asked Questions
Inline inspection is a quality control check performed while production is still in progress, typically when 10% to 60% of the order is complete. It allows inspectors to identify defects, workmanship issues, and specification deviations early enough to correct them before the full batch is finished.
Inline inspection happens during production (10%–60% completion) and focuses on catching problems early so the factory can correct them. Final inspection happens after 100% of production is complete and uses AQL sampling to make a pass/fail decision on the finished lot.
Use inline inspection for large or complex orders, when working with a new supplier, when the product has many assembly stages, or when previous orders from the same factory had quality issues. It is especially valuable when rework costs are high or delivery deadlines are tight.
Most orders require one inline inspection, typically at 20%–40% completion. Large or complex orders may benefit from two: one early in production (10%–20%) and another at midpoint (40%–60%). The number depends on order size, product complexity, and supplier reliability.