Splunk vs Microsoft Sentinel
This is a SIEM-to-SIEM comparison, not a platform swap. Sentinel replaces the security half of Splunk and has two things Splunk does not: a published rate card you can put in a spreadsheet, and a rule translator shipped inside the product. What it asks in return is that your estate already looks like Azure and Microsoft 365.
Pick Sentinel if Microsoft 365 and Defender already sit at the centre of your security estate, if you need a cost model approved before the pilot, and if noisy high-volume sources can live in a cheap data lake tier instead of the analytics tier. Stay on Splunk if it also carries your application and infrastructure logs, if your detections depend on SPL that has no KQL equivalent, or if a multi-cloud estate makes an Azure-shaped SIEM the wrong centre of gravity.
Side by side
Splunk vs Microsoft Sentinel at a glance
| Splunk | Microsoft Sentinel | |
|---|---|---|
| Category | Log platform plus premium SIEM app | SIEM, security only |
| Billing unit | Ingest GB/day, workload compute or entity | GB ingested, by tier |
| Public list price | ✗ none, private offer on AWS Marketplace | ✓ Azure rate card, region-dependent |
| Pay-as-you-go rate | Quoted | Around $4.30/GB analytics |
| Volume discount | Negotiated, invisible | Commitment tiers, up to 52% off PAYG |
| Cheap tier for noisy logs | Federated search and archive | Data lake tier near $0.50/GB |
| Free allowance | 500 MB/day, no alerting, no clustering | Up to 5 MB/user/day for key security logs |
| Query language | SPL | KQL, equally non-portable |
| Rule migration tooling | Not applicable, incumbent | ✓ built-in SPL to KQL migration experience |
| Self-host / licence | ✗ proprietary only | ✗ Azure only, no self-host |
| Cloud neutrality | ✓ runs anywhere, any cloud | ✗ Azure-resident by design |
| Best for | Multi-cloud estates and deep detection engineering | Microsoft-centric security teams with a budget to defend |
Sources: Splunk pricing · Microsoft Sentinel pricing · Sentinel billing docs · SIEM migration experience docs. Rates are Azure list prices and vary by region; check the Azure pricing calculator. Compiled August 2026.
Where Microsoft Sentinel wins
The price is on a page, and it goes down in public
Sentinel's meter is GB ingested, and both the base rate and the discount curve are documented. Pay-as-you-go analytics ingestion runs around $4.30 per GB; commitment tiers cut that as volume grows, roughly $2.96 per GB at 100 GB per day and about $2.31 per GB at 5,000 GB per day, with Microsoft advertising up to 52 percent off pay-as-you-go at the top of the curve. Tiers can be upgraded at any time and downgraded after 31 days. Splunk's own pricing page names three models, Workload, Ingest and Entity, and attaches no number to any of them. Sentinel's rates are Azure list prices and they move by region, so build your case in the pricing calculator rather than from this table; the point is that you can build it at all.
A tier priced for the logs you only keep for compliance
Splunk's cost problem is usually not the detections, it is the firewall and proxy volume nobody searches until an audit. Sentinel's data lake tier is priced for exactly that traffic at roughly $0.50 per GB, an order of magnitude under the analytics tier, and Microsoft's pricing page states it includes 30 days of free storage during preview. Getting the same separation on Splunk means federated search, archive tiers, or a data pipeline product sitting in front of the indexer.
Rule migration ships in the box
The SIEM migration experience translates SPL to Kusto Query Language one rule at a time, accepts both Splunk Enterprise and Splunk Cloud as sources, maps your Splunk data sources onto Sentinel tables and Splunk lookups onto watchlists, resolves macros by inline replacement, and converts Common Information Model field names into the Advanced Security Information Model. Microsoft is refreshingly plain about the limits: translations must be reviewed and adjusted, and anything the tool cannot convert is a manual job. That is still the difference between a review exercise and a rewrite.
If you already pay Microsoft, some of the plumbing is done
Defender, Entra ID sign-in logs and Microsoft 365 audit data connect natively, and the free allowance of up to 5 MB per user per day for key security logs covers a meaningful slice of that traffic. Sentinel is also a Leader in the 2025 Gartner Magic Quadrant for SIEM, the same report where Splunk placed as a Leader for the eleventh consecutive time, so this is not a downgrade in analyst standing; it is a different centre of gravity.
Where Splunk still wins
Splunk does two jobs and Sentinel does one. In most organisations Splunk is where the security team hunts and where a platform engineer greps for a stack trace at 2am. Sentinel is a SIEM; it has no ambition to be your application log search. Replace the SIEM half and you have bought yourself a second procurement exercise for the other half, which is the most common surprise in this migration and the reason teams wanting a single replacement usually compare Splunk against Elastic instead.
The lock-in also does not disappear, it relocates. KQL is exactly as unportable as SPL, and your bill becomes a function of Log Analytics workspace design, table plans and retention settings, which is its own specialism. Splunk runs on your own hardware, in any cloud, or on Splunk Cloud, and a multi-cloud or heavily on-premise estate pays a real tax for routing everything into Azure. On detection depth, Splunk Enterprise Security still brings risk-based alerting and a mature notable-event workflow, and Splunkbase carries add-ons for legacy sources that have no Sentinel connector at all.
Migrating Splunk to Sentinel
The path most teams take:
1. Split the data before you move it. Decide which sources belong in the analytics tier and which are audit-only and belong in the data lake tier. Doing this after cutover is how a Sentinel bill ends up looking like the Splunk bill you left.
2. Connect the Microsoft sources first. They are the cheapest, fastest wins and they exercise your workspace design before the ugliest custom source arrives.
3. Run the migration experience on your rules, then review every one. Start with the detections you trust least, not the ones you trust most, so you find the translation gaps while Splunk is still running behind you.
4. Plan for what stays behind. Historical indexed data does not move without re-ingestion. Dashboards, scheduled reports and every non-security use of Splunk need a separate destination, and the analysts who think in SPL need time on KQL that no tool provides.
Common questions
FAQ: Splunk vs Microsoft Sentinel
How much does Microsoft Sentinel cost compared to Splunk?
Sentinel's rates are Azure list prices and vary by region, but they exist and you can model them. Pay-as-you-go analytics ingestion runs around $4.30 per GB, commitment tiers bring that down as volume rises, roughly $2.96 per GB at 100 GB per day and about $2.31 per GB at 5,000 GB per day, and Microsoft advertises savings of up to 52 percent against pay-as-you-go at the largest tiers. The data lake tier for high-volume low-value logs sits near $0.50 per GB. Splunk publishes no comparable figure for Splunk Enterprise or Splunk Cloud; its AWS Marketplace listing asks you to request a private offer. Check the Azure pricing calculator for your own region before you build a business case.
Can Microsoft Sentinel convert my Splunk SPL rules to KQL?
Yes, and it is built into the product rather than sold as a service. The SIEM migration experience translates SPL to Kusto Query Language rule by rule, supports Splunk Enterprise and Splunk Cloud as sources, maps Splunk data sources onto Sentinel tables and Splunk lookups onto watchlists, replaces macros inline, and translates Splunk Common Information Model field names into the Advanced Security Information Model. Microsoft is explicit that translations must be reviewed and adjusted, and that rules the tool cannot convert have to be translated by hand. It moves detection rules only; dashboards, reports and scheduled searches are a separate job.
Is Microsoft Sentinel a real replacement for Splunk, or only for the security half?
Only for the security half, and you should plan on that. Sentinel is a SIEM: it is built for detection, investigation and response, and it is a 2025 Gartner Magic Quadrant Leader for SIEM. It is not a general log analytics platform for application debugging and infrastructure troubleshooting the way Splunk Enterprise is used in practice. If Splunk carries both jobs at your organisation, moving the SIEM to Sentinel leaves you needing a log platform for everything else, which is why teams that want a single replacement usually land on Elastic instead.