Programmatic Waste and Supply Path Optimisation: A 2026 Guide

When the ANA published its first programmatic transparency study in 2023, the headline was uncomfortable: made-for-advertising (MFA) sites took 15% of programmatic spend, and the average campaign ran across 44,000 websites ¹. Three years on, ANA benchmark data shows real improvement, but also a widening gap between advertisers who manage their supply paths and those who do not.

This guide covers what the data says, what MFA and curation mean in practice, and how supply path optimisation (SPO) can recover wasted budget.

What the ANA found in 2023

The ANA Programmatic Media Supply Chain Transparency Study, released in June 2023, tracked $123m of spend and around 35.5 billion impressions from 21 advertisers ¹. Its main findings:

• MFA sites took 15% of spend and 21% of tracked impressions ¹.
• The average campaign ran on 44,000 websites, though a few hundred well-chosen sites would reach most valued audiences ¹.
• Marketers could save at least $13bn by improving practices and cutting MFA, and up to $20bn by following all of the ANA's recommendations ¹.
• MFA inventory carried 26% higher carbon emissions than other inventory, based on Scope3 data ¹.

The ANA traced the problem to two causes: buyers optimising for cheap impressions, and marketers having less visibility into inventory than sellers ¹. The ANA later estimated around $22bn a year was being lost to MFA, indirect supply paths, invalid traffic and other inefficiencies ².

What has changed since: the ANA benchmark

The ANA now runs a quarterly Programmatic Transparency Benchmark. The trend is positive at the median, but uneven.

Measure	Earlier figure	Latest figure
Median MFA share of spend	2.3%	0.8% (Q2 2025) 3
Active domains	53,799	28,958 (Q2 2025) 3
Private marketplace share of spend	64.5%	87.8% (Q2 2025) 3
ANA TrueAdSpend Index	43.3% (Q1 2026)	45.1% (Q2 2026) 45

Three findings stand out.

The gap between good and poor buyers is widening. In Q1 2026, top performers converted 54.0% of spend into qualified impressions while lower performers converted 32.1%, the largest gap the benchmark has recorded. Top performers paid $7.46 per thousand qualified impressions; lower performers paid $19.04 ⁴. The ANA's CEO Bob Liodice summarised it as "quality, not cost, is the primary differentiator in programmatic performance" ⁴.

MFA has not gone away. While median MFA spend fell to 0.8% in Q2 2025, top-quartile spenders on MFA still put up to 28.7% of spend on MFA domains ³. In Q1 2026, MFA exposure rose to 1.1%, up from 0.4-0.6% through 2025, with the ANA flagging AI-generated "slop" sites as an emerging subtype ⁴. EMARKETER reported in June 2026 that MFA still appears inside supposedly curated private marketplaces ².

Fees still take a large cut. In Q2 2026, transaction costs accounted for 27.2% of spend, partly offsetting quality gains. Higher performers also ran on around 19,000 fewer domains and apps than lower performers ⁵. CTV made up 41.6% of tracked spend in Q2 2026 ⁵, so the same discipline now applies to streaming as well as the open web.

What MFA sites are and why they persist

EMARKETER describes MFA sites as websites built primarily to sell ad impressions rather than serve audiences, typically combining clickbait, heavy ad loads and purchased traffic ². They persist because they can look efficient on surface metrics, and because they are not fraud in the technical sense, so invalid traffic filters do not always remove them. EMARKETER also notes that 45% of marketers were still paying higher CPMs for MFA domains than for non-MFA ones ².

The fix is not a longer blocklist. The ANA's 2023 recommendation was to move from exclusion lists to inclusion lists of sites you have chosen to buy ¹.

Supply path optimisation: the mechanics

SPO means choosing the shortest, most transparent routes between your DSP and the publishers you want, and cutting the redundant resellers in between. The same impression can often reach a buyer through several SSPs and resellers, each taking a fee.

The industry standards that make this possible come from IAB Tech Lab:

• ads.txt lets publishers publicly name the companies authorised to sell their inventory ⁶.
• sellers.json lets buyers look up which companies sell inventory directly or as intermediaries ⁷.
• The SupplyChain object shows every party that sold or resold a specific bid request, so buyers can confirm they are buying as directly as possible ⁷.

The ANA benchmark shows the effect of this work: the median number of SSPs used fell from 19 to 17 in the Q2 2025 benchmark ³.

Curation: useful, but not a free fix

Curation is one of the industry's main responses to open-web quality concerns. Digiday describes it as an umbrella term covering traffic shaping, auction packages, curated marketplaces and SPO ⁸. The latest shift is agencies running curation themselves: in December 2025, Digiday reported that agencies such as Butler/Till were filtering supply from a defined set of SSPs before it reaches the DSP, favouring direct, authorised paths and suppressing resold routes ⁹. Butler/Till said about 80% of its spend now runs through deals ⁹.

The risks are worth stating plainly. Marketers often do not know exactly what a curated package contains until the campaign runs ⁸, each curated layer can add a fee, and as noted above, MFA has been found inside curated private marketplaces ². Curation works when you can see the domains, apps and fees involved.

Practical steps to reduce programmatic waste

1. Get log-level data. Require impression-level reporting from your DSP and agency so you can see domains, apps, SSPs and fees ².
2. Build inclusion lists. Start from sites and apps that reach your audience and review the list quarterly ¹².
3. Cut duplicate paths. Use ads.txt, sellers.json and the SupplyChain object to favour direct routes and reduce the number of SSPs ⁶⁷.
4. Judge cost per quality impression. Track cost per viewable, measurable, brand-safe impression, not raw CPM ⁴.
5. Audit curated deals. Ask for domain lists, fee breakdowns and MFA screening before buying a curated package ⁸⁹.
6. Benchmark yourself. Compare your results against independent benchmarks such as the ANA's.

Key takeaways

• The ANA's 2023 study found 15% of programmatic spend going to MFA sites and campaigns running on 44,000 websites ¹.
• Median MFA spend fell to 0.8% by Q2 2025, but MFA exposure ticked back up to 1.1% in Q1 2026 ³⁴.
• The best advertisers convert 54% of spend to qualified impressions; the weakest only 32% ⁴.
• SPO relies on ads.txt, sellers.json and the SupplyChain object to cut redundant resellers ⁶⁷.
• Curation can improve quality, but only when domains and fees are visible ⁸⁹.

What this means for your brand

• Ask your agency or trading desk for log-level data and a full fee breakdown for every programmatic campaign.
• Replace broad open-exchange buying with an inclusion list and a short list of direct supply paths.
• Measure success on cost per qualified impression and business outcomes, not CPM or click-through rate.
• Treat curated deals as a product to be audited, not a guarantee of quality.

Sources

1. ANA: 15% of programmatic ad spend is wasted on click-bait websites - Marketing Dive, June 2023
2. FAQ on ad fraud: MFA sites, wasted programmatic spend, and how advertisers fight back - EMARKETER, June 2026
3. The ANA Q2 2025 Programmatic Transparency Benchmark Finds $26.8B in Wasted Programmatic Spend - ANA, August 2025
4. ANA Programmatic Transparency Benchmark Reveals Widening Gap Between Top and Bottom Advertisers - ANA, May 2026
5. ANA Programmatic Transparency Benchmark: Q2 2026 Working-Media Efficiency Reaches a Record 45% - Fiducia, August 2026
6. ads.txt - Authorized Digital Sellers - IAB Tech Lab, accessed October 2026
7. sellers.json Supply Chain Transparency - IAB Tech Lab, accessed October 2026
8. The curation conundrum: separating fact from fiction in ad tech's latest obsession - Digiday, December 2024
9. Agencies push curation upstream, reclaiming control of the programmatic bidstream - Digiday, December 2025

Figures and product details are as reported by the sources listed, at the time of writing. Platforms change quickly, so check the latest documentation before acting on any single number.