# Can I bump the traffic allocation partway through a Hydrogen experiment?

Asked by Hannah Berg on 2026-08-26. Tags: hydrogen, experiments, ab-testing.

I started an experiment on a product page on our Hydrogen storefront at a
conservative traffic share because I wanted to limit exposure early. It is
behaving well and I would now like to ramp the allocation up to gather data
faster.

Is changing the traffic allocation mid-flight safe, or does it compromise the
validity of the results? I would rather leave it alone than end up with numbers
I cannot trust.

## 2 answers

### Answer from hannah_cro (2026-08-28)

Leave it alone. The traffic allocation is a percentage you set on the
experiment, say 30% of visitors see the variants across your 2 to 5 variants,
and changing that distribution mid-flight is strongly discouraged because it
invalidates the statistics. Visitors before and after the change are different
populations, and once the split moves those populations get weighted unevenly
across variants, which biases the result. Adding or removing a variant during
the run has the same problem.

For context on when it is even allowed to end: an experiment stays in progress
until each variant has at least 1000 visitors, at least 25 conversions, and has
run at least one week. So a conservative allocation mostly just means it reaches
those thresholds a little later, not that the run is compromised.

### Answer from tomdev83 (2026-08-29)

If gathering data faster is the real goal, the clean path is to restart with
the allocation you actually want rather than ramp the current one. Plan the
split up front on the fresh test and let it run untouched to the thresholds.
You lose the early days of data, but you get a result you can defend, which is
cheaper than finishing a biased run and not being able to use it.

#### Reply from Hannah Berg (2026-08-30)

That settles it. I will stop the current one and relaunch at the higher
allocation from the start rather than touch a running test. Thanks for
confirming the reasoning, not just the rule.