Best Prompt Injection Protection Tools in 2026
Short answer: Lakera is the fastest way to put a filter in front of an app this week, $0/mo on Community for 10,000 requests a month. Prompt Security, now owned by SentinelOne, and Lasso Security fit an enterprise that wants gateway-level enforcement across every model, both sold on a quote. HiddenLayer and Prisma AIRS wrap prompt injection detection inside a wider AI security or network platform. Guardrails AI and WhyLabs LangKit are the free, open-source route for a team that will run the filter itself. Most of this category publishes no public price at all.
Ten filters compared on what they block, where the free tier stops, and what each vendor will put a number on.
A prompt injection filter sits between the user, or the document an agent just read, and the model, and it has one job: catch the instruction that was never supposed to be there. That covers a jailbreak typed into a chat box and the line buried in a PDF an agent summarizes, then quietly obeys.
Toolradar data: of the 719 security tools in the catalog, 49% offer a free or freemium plan, and 356 tools (50%) are paid-only with no public tier at all.
That split matters here because prompt injection defense sits mostly in the paid-only half. Start with Lakera for a filter running today on a free request cap, and read best LLM security tools for the wider red-teaming and runtime picture. Move to Prompt Security or Lasso Security when the buyer is a security team enforcing at the gateway across every app. If the real gap is an agent nobody registered, that inventory problem belongs in AI agent security, since no filter protects a system it never saw.
How we ranked: these 10 were picked from the 719 security tools in the catalog for a direct answer to "does this block prompt injection in production," every price came from the vendor's own page, its AWS Marketplace listing, or its GitHub license this month.
Top Picks
Picked by editorial review, informed by G2 and Capterra review volume and rating and by media mentions, the signals behind our category rankings. How we rate
| Tool | Starting price | Rating | Best for |
|---|---|---|---|
| Lakera | Free (Community) | n/a | Teams that want a working filter today without a sales call |
| Prompt Security | Publishes no list price | n/a | Enterprises that want gateway-level blocking across every model and agent |
| HiddenLayer | No usable list price | n/a | Security teams that also want model scanning and attack simulation in one contract |
| Lasso Security | Publishes no list price | n/a | Teams most worried about indirect injection hidden in files, web pages, or emails |
| Noma Security | Publishes no list price | n/a | Teams whose risk is agents chaining tool calls, not a single chat message |
| Prisma AIRS | Publishes no list price | 4.41,601 reviews | Enterprises already inside the Palo Alto ecosystem that want one more control there |
| Guardrails AI | Free, Platform on quote | 4.329 reviews | Developers who want to own the filter's code instead of routing traffic to a vendor |
| Arthur Shield | Publishes no list price | n/a | Teams already using Arthur for model monitoring that want the firewall in one vendor |
| Ovalix | Publishes no list price | n/a | Teams that need one policy layer across ChatGPT-style tools and their own agents |
| WhyLabs LangKit | Free, open source | 4.627 reviews | Developers who want a no-cost starting point and will tune the model themselves |
Teams that want a working filter today without a sales call
Enterprises that want gateway-level blocking across every model and agent
Security teams that also want model scanning and attack simulation in one contract
Teams most worried about indirect injection hidden in files, web pages, or emails
Teams whose risk is agents chaining tool calls, not a single chat message
Enterprises already inside the Palo Alto ecosystem that want one more control there
This pricing model is best suited for established enterprises with substantial cloud infrastructure and budgets.
Watch out
Minimum credit purchase of 100 credits per tier.
Developers who want to own the filter's code instead of routing traffic to a vendor
Teams already using Arthur for model monitoring that want the firewall in one vendor
Arthur AI's pricing structure is quite generous, especially with its feature-rich Free tier.
Watch out
Professional Services are an add-on
Teams that need one policy layer across ChatGPT-style tools and their own agents
The Enterprise-only pricing with 'Contact sales' is opaque and likely expensive, as it lacks transparent entry-level tiers common in AI security platforms.
Watch out
Custom integration fees not included in base platform
Developers who want a no-cost starting point and will tune the model themselves
WhyLabs shut down.
What a prompt injection protection tool actually does
Prompt injection protection inspects a prompt, a retrieved document, or a tool response before an LLM acts on it, then blocks, flags, or rewrites the ones trying to override the system's instructions. OWASP ranks prompt injection as the top risk on its LLM list, and it works whether the malicious text comes straight from the user (direct injection) or from a web page, email, or file the model reads on the user's behalf (indirect injection).
The detection layer is the whole product for a purpose-built vendor. Lakera screens requests for free up to a published cap and scales to a configurable enterprise plan; Check Point acquired the company in a deal that closed in Q4 2025, and it still ships under the Lakera name. Prompt Security, bought by SentinelOne in a deal that closed September 5, 2025, gives model-agnostic coverage across major LLM providers and names security for more than 13,000 known MCP servers, a detail that matters once agents are calling tools, not one chatbot. Lasso Security runs an "Intent Deputy" that checks intent rather than only keywords, and states 99.83% detection accuracy under 50 milliseconds on its own benchmark.
A wider platform treats the filter as one module instead. HiddenLayer folds Prompt Injection & Guardrails into a suite that also scans model files and simulates attacks; its only public dollar figure is a marketplace listing with an undefined unit, treated here as no usable list price. Prisma AIRS, Palo Alto's runtime layer, lists prompt injection beside data leakage and tool misuse, and its AWS listings route billing through a private agreement rather than a rate card. Guardrails AI and WhyLabs LangKit take the opposite shape: open-source Python libraries wired directly into an app, no vendor filter in between. Testing whether your own defenses hold up is a different purchase, covered in best AI red teaming tools.
Why the price you can quote is rarely the price you pay
The costly mistake here is assuming a number from an adjacent product is the prompt injection price. SentinelOne's own packages page lists Singularity Complete at $179.99/yr per endpoint and Commercial at $229.99/yr, and neither covers Prompt Security, which has no price on that page at all. A buyer already running SentinelOne for endpoint detection still opens a new conversation for the GenAI firewall.
Lakera is the exception. Its free Community plan has a real monthly request cap and a prompt-length limit, and includes the API, dashboards, and EU residency. Cross either line and you are in Enterprise, a sales call for a configurable per-model plan with SSO and self-hosting. HiddenLayer's AWS Marketplace listing shows a seven-figure, 12-month contract that itself states the unit is undefined and tells buyers to confirm how it is counted, treated here as no usable list price rather than a per-model rate. Prisma AIRS has the same shape: its AI Runtime Security listing states plainly that pricing runs through an external billing relationship with Palo Alto.
Arthur is a third pattern. Its base observability platform publishes real tiers, free and $60/mo, with unlimited seats even on the free one, but Arthur Shield, the firewall that flags prompt injections specifically, is a separate product with no price anywhere, so the cheaper platform tiers do not include runtime blocking. The open-source options avoid this trap by construction: Guardrails AI's detect_prompt_injection validator is Apache 2.0 and installs from the Guardrails Hub at no cost, and WhyLabs LangKit is the same, free after WhyLabs open-sourced its stack and stopped selling a commercial platform.
Key Features to Look For
Coverage of direct and indirect injection (Essential)
Lasso Security scans external content such as documents and API responses before an agent reads them, which is where indirect injection hides. A filter that only screens the typed prompt misses the attack coming through a retrieved file.
A deployment point that matches your architecture (Essential)
Lakera and Prompt Security offer a gateway or proxy mode plus an SDK, while Guardrails AI and LangKit are libraries called directly in code. Pick the shape that fits how traffic already routes, or you are rebuilding the pipeline for the vendor.
A published request or token cap on the free tier (Essential)
Lakera Community states its monthly request cap and prompt-length limit precisely, in the pricing table below. A vendor that will not print a cap will not let you size a pilot before a contract.
MCP and tool-call awareness (Important)
Prompt Security names coverage for more than 13,000 known MCP servers, and Noma Security's AI-DR watches the full chain of prompt, tool call, and data access rather than one message alone. Skip this if the estate is one chatbot with no agents.
A named detection method, not just a claim (Important)
Lasso publishes a stated accuracy figure on its own benchmark, and Guardrails AI's validator is built on the open Rebuff library, so the code is readable. A vendor with neither is asking you to trust a black box.
Data residency and self-hosting options (Important)
Lakera Community is EU-only, Enterprise adds EU or US and self-hosted deployments, and the open-source libraries run entirely on your own infrastructure by default. That is a contract term for a regulated buyer, not a nice-to-have.
Latency the app can absorb (Nice to have)
Lasso states detection under 50 milliseconds and Prompt Security advertises real-time blocking; a filter that adds a full second to every model call gets disabled the first time someone complains, whatever it caught.
An honestly documented false-positive rate (Nice to have)
WhyLabs' own documentation for LangKit's injection model flags a known high false-positive rate rather than hiding it, more useful than a vendor number you cannot verify yourself.
What to settle before you pick one
Decide whether the attack surface is a chatbot, a tool-calling agent, or both. Prompt Security and Noma Security are built around agent and MCP coverage; Lakera and Lasso filter a chatbot's inputs without needing tool-call context.
Confirm the deployment shape matches your stack. A gateway or proxy filter needs a routing change; Guardrails AI and LangKit need a developer to call the library inline, faster to pilot and slower to standardize across many apps.
Ask every enterprise vendor for a number before the call ends. Prompt Security, Lasso Security, Noma Security, Prisma AIRS, Arthur Shield, and Ovalix all publish no list price, so the first figure you can plan around is whatever the call produces.
Do not assume an existing security contract covers this. SentinelOne's public per-endpoint packages do not include Prompt Security, and Arthur's cheaper platform tier does not include Shield: both are separate line items.
If you need a filter running this week and can live inside a 10,000-request monthly cap, Lakera Community and the two open-source libraries are the only options with no purchase order at all.
Evaluation Checklist
Test the filter against both a typed jailbreak and a document-borne instruction (indirect injection); a vendor demo often only shows the first.
On Lakera, confirm traffic stays under Community's monthly request cap and its prompt-length limit before building on it, or budget for Enterprise from day one.
On Prompt Security, ask which MCP servers and self-hosted models are covered today versus on a roadmap, since the published server count is a catalog, not a guarantee for your stack.
On HiddenLayer, get a written definition of what one marketplace unit maps to (model, agent, or endpoint) before treating any figure on that listing as a per-seat price.
On Prisma AIRS, ask whether AI Runtime Security rides on an existing Palo Alto license or needs a new billing relationship, since the AWS listing has no rate card.
On Arthur, confirm in writing whether the quote covers Shield specifically, since the public pricing page prices the observability platform, not the firewall.
If piloting Guardrails AI or LangKit, benchmark the false-positive rate on your own traffic before production, since both are documented as imperfect out of the box.
Pricing Overview
Free and open source
Lakera Community's capped API, and the Guardrails AI and WhyLabs LangKit libraries you self-host.
$0
Enterprise, quote-only
Prompt Security, Lasso Security, Noma Security, Prisma AIRS, Arthur Shield, and Ovalix, all sold after a sales call.
Custom quote
Marketplace listing, undefined unit
HiddenLayer's AWS contract, which states its own unit is undefined and tells buyers to confirm the count with the vendor first.
No usable list price
Pricing Comparison
| Tool | Published price | What that price buys | Billing |
|---|---|---|---|
Lakera | $0/mo Community | 10,000 requests/mo, prompts to 8,000 tokens, API and dashboards. | Free, then quote |
Publishes no list price | Owned by SentinelOne since Sep 5, 2025. Not in Singularity packages. | Quote | |
No usable list price | AWS listing is a 12-month contract with an undefined unit. | Marketplace, undefined unit | |
Publishes no list price | Gateway, SDK, or API deployment; 99.83% accuracy is the vendor's own figure. | Quote | |
Publishes no list price | AI-DR runtime protection plus agent and MCP discovery. | Quote | |
Publishes no list price | AWS listing states billing runs through an external Palo Alto agreement. | Quote, external billing | |
Free, open source | detect_prompt_injection validator is Apache 2.0; Platform adds evals and hosting on quote. | Free, or quote | |
Publishes no list price | Firewall is separate from Arthur's free and $60/mo observability tiers. | Quote | |
Ovalix | Publishes no list price | Real-time policy enforcement across public, homegrown, and agentic AI. | Quote |
Free, open source | Apache 2.0 Python toolkit; WhyLabs no longer sells a commercial platform. | Free |
Prices verified September 2026 on Lakera pricing, SentinelOne platform packages, Arthur pricing, and the detect_prompt_injection and WhyLabs LangKit repositories. HiddenLayer and Prisma AIRS figures come from their AWS Marketplace listings, not a vendor pricing page. See security for the wider catalog and best AI agent security tools for the inventory problem behind an unregistered agent.
Mistakes to Avoid
- ×
Assuming an existing SentinelOne contract already covers Prompt Security. The Singularity endpoint packages are a different product; Prompt Security is a separate acquisition with its own quote.
- ×
Reading HiddenLayer's or Prisma AIRS's marketplace figure as a per-model price. Both listings either leave the unit undefined or route billing through an external agreement, so neither number is a rate you can multiply by seats.
- ×
Budgeting Arthur's cheaper platform tier as if it includes Shield. That tier is the observability platform; the firewall that flags prompt injection is priced separately, with no public number.
- ×
Testing only typed jailbreaks and skipping indirect injection. Lasso and Prisma AIRS both specifically call out document- and tool-response-borne attacks, and a filter that only screens the chat box misses that entire path.
- ×
Deploying Guardrails AI's archived detect_prompt_injection repository instead of the maintained Hub monorepo. The old repo still installs, but issues and fixes now land in a different location.
- ×
Trusting a vendor's own accuracy number without a proof of value. Lasso's benchmark and LangKit's documented false positives are both real, first-party figures, but they describe different vendors' own tests, not an independent one on your traffic.
Expert Tips
- →
Start free and cap it deliberately. Lakera Community's request and token limits are generous enough for a real pilot; hit the wall on purpose before calling sales, so you know exactly what Enterprise needs to solve.
- →
Ask every quote-only vendor the same three questions. Price per request or seat, what counts as a unit, and whether MCP or agent coverage is included today. Prompt Security, Lasso, Noma, Prisma AIRS, Arthur Shield, and Ovalix will otherwise quote on their own terms.
- →
Pair a filter with an inventory, not instead of one. A runtime block on Lakera or Lasso only protects the app you registered; the unregistered agent problem is best AI agent security tools.
- →
Get HiddenLayer's marketplace unit defined in writing before a pilot. The listing tells you to do this yourself, so treat that instruction as the first step, not a formality.
- →
Run the open-source options against your own red-team prompts first. Guardrails AI and LangKit cost nothing to test, and LangKit's documented false-positive issue is exactly what a quick internal test surfaces before production.
- →
Do not average a marketplace figure into a per-tool budget. HiddenLayer's undefined-unit listing and Prisma AIRS's externally billed API are not comparable to Lakera's flat free tier, and the wider catalog is security.
Red Flags to Watch For
- !
A SentinelOne quote that assumes Prompt Security rides along with an existing Singularity Complete or Commercial contract without a separate line item.
- !
A HiddenLayer or Prisma AIRS proposal that treats a marketplace listing's dollar figure as a per-model or per-seat price without a written definition of the unit.
- !
An Arthur quote that prices the cheaper observability tier and calls it Shield coverage.
- !
A vendor demo that only shows a typed jailbreak prompt and never a document- or tool-response-borne attack, which is most of what indirect injection looks like in production.
- !
Any vendor in this category citing a third-party benchmark number instead of a figure on its own site, when this guide could not verify that number first-party either.
The Bottom Line
Lakera when you want a filter live today and can work inside a 10,000-request Community cap. It is the one product on this list with a real, checkable free price, and Check Point's backing since the deal closed in Q4 2025 means the product is not going away.
Prompt Security or Lasso Security when the buyer is a security team that wants gateway-level enforcement across every model and agent, and can absorb a sales cycle to get a number. Prompt Security's edge is MCP-server coverage claimed at more than 13,000, a SentinelOne figure; Lasso's is a stated, checkable accuracy figure and document-level scanning.
HiddenLayer or Prisma AIRS when prompt injection defense should sit inside a broader AI security or network platform you already run, and you accept that neither vendor prints a usable price before the call. Guardrails AI and WhyLabs LangKit when the team would rather own free, auditable code than route traffic through anyone's proxy, and will tune the detector's known rough edges itself. Noma Security, Arthur Shield, and Ovalix round out the enterprise quote-only tier, each with a different starting point: agent behavior, an LLM firewall next to model monitoring, and one policy layer across public and homegrown AI.
Cite this: Toolradar, "Best Prompt Injection Protection Tools in 2026," September 2026. Prices checked on vendor pages, AWS Marketplace listings, and GitHub license files in September 2026. Compared against the 719 security tools we track.
Frequently Asked Questions
What is the best prompt injection protection tool in 2026?
Lakera, if you want a filter running this week without a sales call: Community is free within its monthly request cap. Choose Prompt Security or Lasso Security for gateway enforcement across every model and agent an enterprise runs, both on a quote. Choose HiddenLayer or Prisma AIRS if the filter should live inside a wider AI security or network platform, or Guardrails AI and WhyLabs LangKit if you would rather own free, open-source code than send traffic through a vendor's proxy.
How much does prompt injection protection cost in 2026?
Lakera is the clearest answer: free for Community within its request cap, then a quote for Enterprise beyond it. Guardrails AI's detect_prompt_injection validator and WhyLabs LangKit are also free, open-source libraries you self-host. Prompt Security, Lasso Security, Noma Security, Prisma AIRS, Arthur Shield, and Ovalix publish no list price at all, every one a sales conversation. HiddenLayer's only public figure is a 12-month AWS Marketplace contract with an undefined unit, treated here as no usable list price. SentinelOne's endpoint packages and Arthur's cheaper platform tier do not include this category's product, so neither stands in for its price.
Is there a free prompt injection protection tool?
Yes, three of them. Lakera Community is free for 10,000 requests a month and an 8,000-token prompt, with the API, dashboards, and EU residency included. Guardrails AI's detect_prompt_injection validator and WhyLabs LangKit are both Apache 2.0 libraries at no cost, though you run and maintain them yourself. Every other tool here, Prompt Security, HiddenLayer, Lasso Security, Noma Security, Prisma AIRS, Arthur Shield, and Ovalix, is enterprise-only with no published free tier.
What is the difference between direct and indirect prompt injection?
Direct injection is an instruction typed straight into the chat box, trying to override the system prompt. Indirect injection is the same kind of instruction hidden inside content the model reads on the user's behalf, a web page, an email, a PDF, or a tool's API response, so the user never sees it. Lasso Security and Prisma AIRS both scan external content before an agent processes it, the control that catches indirect injection; a filter that only checks the user's own message misses this path entirely.
Does an existing SentinelOne or Arthur contract already cover prompt injection?
Not automatically. SentinelOne's public Singularity packages, Complete at $179.99/yr and Commercial at $229.99/yr per endpoint, are endpoint detection products; Prompt Security, acquired September 5, 2025, is priced as a separate line even for an existing customer. Arthur's public tiers cover model monitoring, and Arthur Shield, the firewall that flags prompt injection, has no published price on either the pricing page or its own product page, so confirm it is on the order first.
How does Guardrails AI compare with a vendor like Lakera?
Guardrails AI is a free, Apache 2.0 Python library: install detect_prompt_injection from the Guardrails Hub and call it in your own code, no vendor in the traffic path and no request cap. Lakera is a hosted service instead, requests go to its API, and Community caps out before Enterprise takes over. Want a managed dashboard without writing detection code? Lakera is the faster start. Want free code you control end to end? Guardrails AI is the fit.
Cite this page: Toolradar, "Best Prompt Injection Protection Tools in 2026", updated September 2026, https://toolradar.com/guides/best-prompt-injection-protection-tools
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