Is CompStak or CoStar better for comps?

It depends on the job. CompStak wins on lease-comp depth — it's a crowdsourced exchange built specifically for transaction-level lease detail: actual signed rents, free-rent and TI concession packages, lease terms, escalations, and tenant names. That makes it the stronger tool for effective-rent analysis in office, retail, and industrial underwriting. CoStar wins on breadth and analytics — it covers virtually every U.S. commercial market with properties, comps, availability, ownership data, and submarket analytics. Most institutional firms that do serious comps work license both: CoStar as the baseline market-scan layer, CompStak for the rent-comp truth that underwriting hinges on.

What is the difference between CompStak's and CoStar's data models?

CompStak runs on a crowdsourced exchange: brokers, appraisers, and researchers contribute verified lease and sales comps and earn credits that unlock access to the broader dataset, with paid enterprise plans also available. The result is unusually deep transaction-level lease detail. CoStar uses a proprietary, field-collected research model — its own large research operation builds the dataset, which is why its coverage is the broadest in the market. The practical upshot: CompStak's depth is concentrated where contribution is active (major metros), while CoStar's breadth extends into secondary and tertiary markets.

Can I connect CompStak or CoStar to my underwriting model automatically?

They behave very differently. CompStak is customer-licensed: you can move the comps your firm is entitled to — via your own CSV/Excel exports, or a provisioned enterprise data feed if your agreement includes one — into your model, and automation can normalize and write them in. No scraping, no redistribution outside your licensed seats. CoStar is works-alongside only: there is no sanctioned API and its terms prohibit automated access, so nothing can pull from CoStar programmatically. The compliant pattern for CoStar is to automate the workflow around it — enriching and assembling from the facts your analysts manually log in your own systems — never to connect to it.

Does CoStar have an API I can use to pull comps?

No. CoStar has no sanctioned public API, and its terms of service expressly prohibit automated or programmatic access — which CoStar actively enforces. Any product claiming a 'CoStar connector' or comp feed is misrepresenting what is technically and legally possible, and using a scraper puts your subscription at risk. The only compliant approach is works-alongside: your licensed team uses CoStar manually, and automation acts on the data you choose to bring into your own tools. There is no automated path to pull CoStar comps.

How does CompStak's crowdsourced model affect access and pricing?

CompStak's exchange lets you earn access by contributing comps (you receive credits that unlock the wider dataset) and also offers paid enterprise plans. For some teams — especially brokerages and appraisers who already generate comps — the contribution path can provide access before committing to an enterprise license. Programmatic or enterprise-feed access exists for certain customers but is gated behind agreements with defined scope and redistribution terms. In all cases, comps are licensed to your firm and may not be redistributed outside your licensed seats.

What's the best comps stack — should I use other tools alongside CompStak and CoStar?

For most firms, yes. CompStak for lease comps and effective rents, CoStar for breadth and analytics, and then adjacents to round it out: Reonomy for off-market ownership intelligence, ATTOM for parcel/tax/deed data via a documented API, and Cherre to unify everything you license into a single data layer. The data sources don't overlap perfectly, so a real comps stack blends them. An aggregation-and-normalization layer on top keeps the comps you're licensed to use flowing into your models and dashboards without manual re-keying.

Where does AI add value if CoStar can't be connected and CompStak is gated?

AI adds value on the data you're licensed to use, in the places your team makes decisions. With CompStak's licensed exports or feed, AI normalizes concessions to a clean effective-rent basis, scores comparability against the subject asset, and drafts an IC-ready rent-support narrative — compressing hours of analyst work into a reviewable draft. With CoStar, AI never touches the platform; instead it runs on the facts your analysts manually log, enriching records from your own licensed sources and assembling briefs and IC packets from your own data. The value is removing the manual relay around the comp source — not a forbidden pipe into anyone's database.

Is it compliant to automate around CompStak and CoStar?

Yes, when done correctly. For CompStak, automation operates only on the comps your firm is licensed to access — your own exports or a provisioned enterprise feed — with no scraping, no bypassing the contribution model, and no redistribution outside your licensed seats. For CoStar, automation never connects to, queries, scrapes, or extracts anything; every workflow is triggered by a human action in your own systems and acts only on data already there. Both approaches keep the licensing and terms-of-service boundaries intact by design — which is exactly how NextAutomation builds these integrations.

CompStak vs CoStar for Comps: Crowdsourced Lease Data vs the Incumbent (2026)

Ask two acquisitions analysts which comp source they trust and you'll often get two answers: one swears by CoStar because it's the platform everyone in the firm already opens; the other swears by CompStak because it's where the real signed-lease economics live. They're both right, and they're not actually describing the same product. CoStar is the broad market-data incumbent. CompStak is a focused, crowdsourced lease-comp exchange. For comps work specifically, the question isn't which one is better — it's which one wins for the job in front of you.

This guide compares CompStak and CoStar for comps the way a research or valuation lead would actually evaluate them: depth of lease detail, breadth of coverage, how access works, and what each costs you in analyst time. We name a winner per use case — and they're genuinely different tools, so the honest answer is frequently "both, for different things." We also cover the adjacent data layer (Reonomy, Cherre, ATTOM) that rounds out a real comps stack.

One positioning note up front: NextAutomation is not a comp dataset and isn't competing with either of these. We're the AI/automation layer that aggregates and normalizes comps you're already licensed to use — pulling them into your models, dashboards, and IC briefs. We'll tell you plainly where CompStak and CoStar each win. This guide is objective first.

CompStak vs CoStar at a Glance

Dimension	CompStak	CoStar
Core strength	Transaction-level lease comps: signed rents, free rent, TI, escalations, terms	Breadth — properties, comps, availability, tenant/ownership, submarket analytics
Data model	Crowdsourced exchange (contribute comps, earn credits) + enterprise licensing	Proprietary research + field-collected dataset
Effective-rent detail	Deep — concessions broken out, built for effective-rent analysis	Present, but comp depth varies by market
Coverage	Strong in major office/retail/industrial metros; thinner in secondary/tertiary	Broadest — virtually every U.S. commercial market
Access / integration tier	Customer-licensed; gated enterprise data feed; no redistribution	Works-alongside only — no sanctioned API, no scraping (ToS-prohibited)
Best for	Underwriting & valuation where lease economics drive the number	Market scanning, sourcing, analytics, broad coverage

The one-line verdict: CompStak wins on lease-comp depth and effective rents; CoStar wins on breadth and analytics. Most institutional firms that do serious office/retail/industrial work end up licensing both — CoStar as the baseline market layer, CompStak for the rent-comp truth that underwriting hinges on.

Buyer Decision Criteria

Before you pick (or renew), score each tool against the criteria that actually move your comps workflow:

Lease-comp depth vs. coverage breadth. Do you need the deepest possible detail on signed leases in a handful of core metros (CompStak), or the widest net across many markets including secondary/tertiary (CoStar)? This is the central tradeoff.
Effective rent vs. face rent. If your underwriting lives or dies on effective rents net of free months and TI, CompStak's concession-level detail is the differentiator. Asking rents alone will flatter every deal.
How you'll get the data out. CompStak is customer-licensed and gated, but enterprise feeds exist for authorized customers. CoStar has no sanctioned API at all — everything is manual export under your license. This shapes what automation is even possible.
Team workflow. CoStar is likely already open on every analyst's screen as the market-scan tool. CompStak is the deeper dive when a deal gets real. Match the tool to where in the funnel the work happens.
Budget reality. Both are meaningful line items. CoStar's enterprise pricing is broad-spectrum; CompStak's crowdsourced model lets some teams access comps via contribution credits before paying for an enterprise plan.

Honest Head-to-Head: Who Wins Per Use Case

Lease-comp depth and effective rents → CompStak

CompStak is purpose-built for exactly the input that drives office, retail, and industrial underwriting: actual signed rents with free-rent and TI concession packages, lease terms, escalations, and tenant detail. Asking rents are marketing numbers; what matters is the effective rent after concessions, and CompStak's crowdsourced exchange surfaces transaction-level detail that rarely appears in headline listing data. For a valuation or underwriting team building a defensible rent-comp set, CompStak is the winner.

Breadth, coverage, and analytics → CoStar

CoStar is the incumbent because it covers virtually every U.S. commercial market with properties, sale and lease comparables, availability, tenant and ownership data, and submarket analytics. For market scanning, screening across many geographies, and the broad context that frames a deal, CoStar's breadth is unmatched. If your work spans secondary and tertiary markets where crowdsourced contribution is thinner, CoStar is the winner on coverage.

Sourcing and market scanning → CoStar (with adjacents)

When the job is "find candidates and understand the submarket," CoStar's breadth plus ownership/availability data wins. Pair it with ownership-intelligence tools when you need to skip-trace owners — see our CoStar vs Reonomy comparison for the property-intel-vs-ownership-data split, and CoStar vs Crexi for the marketplace-coverage angle.

Valuation and IC support → CompStak (for rent), CoStar (for context)

A defensible valuation needs both: CompStak's signed-lease comps for the rent conclusion and CoStar's submarket analytics for the surrounding narrative. This is the clearest "use both" case — and it's where the manual relay between the two platforms costs analysts the most time.

How Access Actually Works (Read This Before You Wire Anything)

The honesty that protects your firm: these two platforms have fundamentally different access models, and getting this wrong is a compliance and contract risk.

CoStar is works-alongside only. CoStar has no sanctioned public API, and its terms of service expressly prohibit automated or programmatic access — and CoStar enforces that. There is no compliant "CoStar connector," no scraping, no automated login. Any vendor claiming a direct CoStar pipe is misrepresenting what's technically and legally possible, and they're putting your subscription at risk. The only compliant pattern is: your team uses CoStar normally under your own license, and automation runs beside it — acting on the facts your analysts choose to bring into your own systems. See the CoStar works-alongside integration for exactly how that boundary is built.

CompStak is customer-licensed and gated. CompStak's access comes through its crowdsourced contribution-and-credit model and/or a paid enterprise plan. Programmatic or enterprise-feed access exists for certain customers but is gated behind agreements with defined scope and redistribution terms — and comps may never be redistributed outside your licensed seats. Automation here operates only on the comps your firm is licensed to use, via your own exports or a provisioned feed. No scraping, no bypassing the contribution model, no redistribution. The CompStak customer-authorized integration documents the data-extraction approach.

Net: with CompStak, a compliant data feed is possible for authorized customers. With CoStar, there is no feed — only manual, human-in-the-loop usage. That difference dictates what you can automate.

The Adjacent Comps Stack

CompStak and CoStar don't cover the whole comps and property-data picture. Three adjacents that round out a real stack:

Reonomy — off-market property and ownership intelligence (now part of Altus). Strongest on the "who owns it and what it sold for" layer. Customer-licensed, partner-gated API with redistribution restrictions. Read CoStar vs Reonomy for the head-to-head.
Cherre — a CRE data-unification platform built as an integration layer. It doesn't replace comp sources; it connects and normalizes the data sources you're licensed to use into a single warehouse-style layer.
ATTOM — property characteristics, tax, deed, and transaction history with a documented, integrator-friendly API (native-api tier). The most automation-friendly of the adjacents for parcel and ownership enrichment.

In practice: CompStak for rent comps, CoStar for breadth, Reonomy/ATTOM for ownership and parcel data, and Cherre to unify whatever you license. For the full landscape, see our pillar guide to the best CRE market data and comps platforms.

Where AI Changes the Answer

Whichever you license — CompStak, CoStar, or both — the bottleneck isn't the data. It's the manual relay between the comp source and the model. An analyst opens the platform, filters a submarket, eyeballs a dozen comps, and retypes the relevant ones into the rent-comp tab. It's slow, error-prone, and impossible to keep current across a live pipeline. This is where a comp-aggregation and normalization layer earns its keep.

With CompStak (customer-licensed feed/export): automation can take your licensed comps, normalize concessions to a clean effective-rent basis, score comparability against the subject, and drop a sourced, attributed comp table straight into the model. Our AI underwriting copilot turns a raw comp export into a ranked, reasoned starting point — the analyst judges comparability instead of transcribing numbers.

With CoStar (works-alongside only): automation never touches CoStar. Instead, property enrichment rounds out the records your team manually logs from CoStar — using your own licensed and integrator-friendly sources like ATTOM — and assembles the surrounding brief and IC packet from your own data. The CoStar boundary stays fully intact.

The honest positioning: NextAutomation is the normalization and automation layer, not the #1 comp dataset. CompStak and CoStar own the data; we move and synthesize the comps you're licensed to use, compliantly, into the places your team makes decisions. For the bigger picture, see the complete CRE software stack.

Lifecycle Fit: Where Comps Show Up

Sourcing: CoStar's breadth scans the market and surfaces candidates; ownership adjacents (Reonomy/ATTOM) identify whom to approach. Property enrichment rounds out each logged target.
Underwriting: CompStak's effective-rent comps drive the rent assumption — the single highest-leverage input. Normalization automation drops a clean comp set into the model.
IC & diligence: Both feed the memo — CompStak for the supportable rent and its driving comps, CoStar for submarket context. The underwriting copilot assembles the rent-support section for GP review.
Asset management: Comp-freshness monitoring keeps valuation assumptions tied to the latest signed deals you're licensed to see, instead of last quarter's pull.
Capital raise & LP/IR reporting: Defensible, attributed comps make rent assumptions auditable for LPs and lenders — the same normalized comp set that backed underwriting backs the investor narrative.

The Bottom Line

For comps specifically: CompStak wins on lease-comp depth and effective rents; CoStar wins on breadth, coverage, and analytics. They're different tools for different jobs, and the institutional answer is usually both — CoStar as the baseline market layer, CompStak for the rent-comp truth underwriting depends on. Neither is dethroned by automation; both are made far more useful by it.

Where NextAutomation fits is the layer above: aggregating and normalizing the comps you're licensed to use into your models, dashboards, and IC briefs — compliantly, with full attribution, and without ever scraping CoStar or redistributing CompStak. If you want to map which comp-automation gives your firm the fastest payback given what you already license, our free roadmap call is the place to start.