How Reddit autobidding chooses
Lowest Cost chases volume inside budget; Cost Cap defends efficiency at delivery cost. This guide picks between them.
Reddit automated bidding centres on Lowest Cost, which seeks as many results as possible within budget, and Cost Cap, where advertisers name a per-result cap for greater cost control. Reddit expanded autobidding to Traffic, Conversions, App Installs, Catalog Sales and Lead Generation in November 2025.
Lowest Cost: volume#
Lowest Cost spends the budget where results come cheapest, maximising conversions or traffic without a ceiling per result. Start here for the first one to two weeks to establish baseline CPA data, then decide whether efficiency needs defending. Reddit advertising costs guide frames it as the volume-first autobid.
Cost Cap: efficiency#
Cost Cap holds average cost per result near your number but throttles delivery when the auction cannot clear it: restrictive caps starve learning and stall spend. Set caps from measured baselines, never aspirations, and loosen when delivery dies. No universal recommended cap exists in Reddit public material. Launch note: autobidding launch.
The progression#
Lowest Cost for 7 to 14 days to learn true costs, Cost Cap once baseline CPA exists, manual bid tweaks only where autobid ranges prove wrong. Switching strategies restarts learning, so commit per phase and judge per phase. Learning mechanics: the learning phase.
Signal requirements#
Both strategies need conversion signal for conversion goals: Pixel plus CAPI, deduplicated, with enough weekly events to learn from. Thin-signal accounts should optimise to traffic or clicks honestly rather than starve a conversion bidder. Foundation: CAPI guide.
MAX as third option#
MAX automates bidding alongside targeting, creative and placements for Traffic and Conversions. Consider it after manual-plus-autobid baselines exist, tested side by side like any challenger. Full comparison: MAX campaigns.
Putting autobidding into practice#
Run Lowest Cost for two weeks on every new conversion group, record the baseline CPA, then graduate half the budget to Cost Cap set 10 per cent above baseline. Compare delivery and efficiency over the next fortnight; the winner takes the account default. Baselines beat opinions.
Revisit caps monthly as auction density shifts: caps set in quiet months starve busy ones. Calendar the review beside budget planning. Progression: the learning phase and budget guidance.
Frequently asked questions#
What is Lowest Cost bidding?
Reddit autobid seeking maximum results within budget, the volume-first option for establishing baselines.
What is Cost Cap bidding?
Autobid holding average cost per result near your cap, trading delivery volume for efficiency control.
Which should run first?
Lowest Cost for 7 to 14 days to learn true costs, then Cost Cap once baseline CPA exists.
Why is my Cost Cap campaign not spending?
Restrictive caps throttle delivery; loosen toward measured baselines until spend flows.
Which objectives support autobidding?
Traffic, Conversions, App Installs, Catalog Sales and Lead Generation since November 2025.
What cap should Cost Cap start at?
Around 10 per cent above measured Lowest Cost baseline CPA.
Read more on this topic#
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