Most teams move to bulk shipping labels to solve a clerical problem, and I understand the appeal completely. Four hundred orders in the queue, somebody clicking through them one at a time, and an obvious fix sitting right there. Print them all at once.

That fix works. What I find more interesting is what it leaves untouched.

Batching groups orders so one operation covers all of them, which means one carrier decision covers all of them too. Most batch workflows get built to assign a single carrier per group, because that is the simplest rule to write and because nobody goes back to a rule that appears to be working. Speed up the batch and you apply that same rule to more shipments.

None of that is baked into bulk labels. It is a choice about how the group gets built, and you can change it. Below is the workflow, where the carrier decision actually gets made, and what it costs your warehouse to move it.

What are bulk shipping labels?

Bulk shipping labels are carrier labels generated for many shipments in one workflow and consolidated into a single file for printing. Orders can arrive from a store integration, a CSV upload, or an API call. Depending on the system, every shipment in the group can follow one carrier rule or be rated and assigned individually.

You will also see them called batch shipping labels. The terms are interchangeable.

Two different problems hide under that one name. Bulk label printing is a print-job problem: one file, one printer, one pass, nobody walking back to a desk between packages. Bulk label buying is a purchasing problem, because every label in that file represents a rate somebody selected and money somebody spent. Most teams get very good at the first and never audit the second.

The mechanics are the same whether you print shipping labels in bulk through a dashboard or through an API. Orders come in, the shipment data gets validated, rates come back for each shipment, a carrier and service get selected, postage gets purchased per shipment, and the finished labels get consolidated into one file for the printer. Manual and automated shipping labels are identical in that sequence except at the selection step. A person picks order by order, a static rule picks once for the whole group, or selection logic picks per package. All three look the same coming off the printer.

Where the carrier decision actually gets made

Picture a batch of 500 orders grouped by pick location and service level, all assigned to one carrier because that is how the group was built. Inside it sit an 8-ounce package going to a dense metro zone and a 6-pound package going to a rural address in zone 7. Those two shipments have almost nothing in common except the hour they were picked. They get the same carrier anyway.

Neither label looks wrong, and that is what makes this one hard to catch. The batch printed cleanly, the packages moved, and nobody filed a ticket. Nothing is broken, so there is no error to go find. There is only a choice that got made once and then inherited a few thousand times.

Reconciliation will show you what you spent. It cannot show you what a different eligible carrier would have charged, because the carrier you never priced left no record behind. So the cost of a group-level carrier rule accumulates in a place your reporting does not cover, which is how a number gets large enough for finance to ask about and still has nothing anyone can point to.

Radio Flyer is a useful reference here. The team went from shipping 800 to 1,000 packages a day to roughly 4,000, integrated in one to two months, and started batch shipping by uploading 250 shipments in a single CSV through the EasyPost API. Throughput is the half of that story a case study can measure. What those 4,000 labels cost against what they could have cost is the half you measure inside your own operation.

What spreading a batch across four carriers costs your warehouse

Every operations lead who has worked a peak season already knows this part, so I will not pretend it is free. A batch that spans four carriers means separate staging lanes, separate pickup windows against however many dock doors you actually have, and separate manifests.

That last one is fixed. A ScanForm can only include shipments from a single carrier account, and every shipment on it has to share the same origin address. So a four-carrier batch is four ScanForms, and somebody has to generate, print, and hand off each one at the end of every shift. If your outbound area is one bench and one door, per-shipment rating can add labor faster than it removes freight cost.

There is a contract version of the same problem. If your carrier agreement has volume tiers, moving shipments off your primary carrier can pull you under a tier break, and the discount you lose can exceed the rate spread you just captured.

Grouping by carrier is not automatically the wrong call. The trouble is that most teams never set that break-even point on purpose. The workflow was built that way three years ago and nobody has revisited it since.

How to tell whether per-shipment rating is worth it

You can size this up before you change anything, using data you already have.

Take last quarter’s shipments and price them against every carrier you could have used. That gives you the rate spread you left on the table, which is the upside. Then subtract the two costs of capturing it: the tier discount you would put at risk once volume moves off your primary carrier, and the labor of running more manifests and more pickups every shift.

If the spread is thin and your contract has a cliff you would fall off, leave the grouping alone and spend the effort somewhere else. If the spread is wide and your dock can absorb another lane, you have a case worth building. Most teams have never run that subtraction, which is why the answer keeps defaulting to whatever the workflow already does.

One API, every carrier in your batch

See how EasyPost rates each shipment on its own attributes, buys postage across 100+ carriers, and returns one print file for the whole batch.

Explore the Shipping API

Five rules I would apply before changing your batch logic

Group by fulfillment constraint. Pick location, service level, and cutoff time are boundaries your operation already has. Carrier selection belongs after the group exists.
Rate every shipment on its own attributes. Weight, dimensions, destination zone, and delivery window should drive selection per package. A multi-carrier shipping API handles the rating and buying across your enabled accounts, and a decision layer like Luma AI Select applies the choice at the moment each label is created, scoring carriers on delivered performance instead of published transit times. EasyPost measures an average of 15% cost savings for customers running Luma.
Keep the print step to one pass. A group spanning several carriers should still come back as a single file, so the person at the printer does one job regardless of how many carriers the batch touched.
Design the exception path. Decide in advance what happens when one shipment has a bad address, a missing weight, or a failed purchase. On EasyPost, every shipment has to reach a purchased state before the consolidated label will generate, so one bad record has to be corrected or pulled out before the rest can print. Find out whether your team can do that in minutes. Almost nobody asks about this during an evaluation, and it is the first thing that bites in December.
Reconcile the batch against delivered performance. Cheapest at purchase and best at delivery are different rankings, and rules tuned only on the first will drift away from the second.

Bulk shipping label FAQs

How many shipments should go in one batch? EasyPost recommends keeping each batch under 1,000 shipments, which avoids timeout errors during the buying process. Above that, split the work into multiple batches. The consolidated labels come back in PDF, ZPL, or EPL2, whichever your printers expect.

Can one batch produce labels for multiple carriers in a single file? Yes. Once the shipments in a group have purchased postage, a consolidated label file can be generated across all of them regardless of which carrier each one used. Your carrier mix does change your manifests, which is a separate constraint worth planning for.

Do I need an API, or is a bulk upload enough? A CSV upload covers teams whose orders live in spreadsheets or arrive from a source with no direct integration. An API earns its place once labels need to be generated on a schedule, triggered by order events, or rated per shipment without a person starting the run. Volume matters less here than how much of the process you want running without a human in it.