Try an AWS CLI --query expression on saved JSON output before running the command
Runs in your browser. Nothing you type is sent anywhere. Checked against sources on 17 Oct 2026.The AWS CLI --query option takes a JMESPath expression, and getting one right by rerunning a slow command is tedious. Save the output once with --output json, paste it here, and shape the expression until the result is what you want, such as Reservations[].Instances[?State.Name == 'running'].InstanceId. Every one of the 892 published JMESPath test cases passes, so the answer matches the CLI.
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JMESPath selects and reshapes JSON with one short expression. The AWS CLI, the Azure CLI, Ansible's json_query filter and many SDKs use it, so the same skill pays off in several places. Getting an expression right by rerunning a slow cloud command is painful; here you paste the saved output once and try as many expressions as you like.
Errors you can act on. A syntax mistake is reported with the character where the parser stopped. A wrong argument says which function and which argument, such as "length(): argument 1 must be string or array or object, not number." A query that matches nothing returns null, as the CLI prints it.
JMESPath or JSONPath? The two look alike but differ: JMESPath filters use [?a == 'x'] with backticks for JSON literals and can build new objects, while JSONPath starts with $. For JSONPath, use the JSONPath Tester.
The rest of the article, and all 6 questions about JMESPath Tester, are on the JMESPath Tester page.
JMESPath queries JSON: it picks fields, filters arrays and builds new objects in one expression. The AWS CLI and Azure CLI use it for their --query option, Ansible uses it in the json_query filter, and SDKs in Python, JavaScript, Go and Java ship it for searching API responses.
Both project over an array, but [] also flattens one level of nested arrays. Reservations[*].Instances[*].InstanceId gives a list of lists, while Reservations[].Instances[].InstanceId gives one flat list, which is usually what an AWS CLI query needs.
Yes for the query itself. The AWS CLI evaluates --query with the Python JMESPath library, and this tester passes the same 892 compliance tests that library passes. Paste output saved with --output json so the data matches what the CLI filters.
No. Parsing the JSON and running the expression both happen in your browser tab, and nothing you paste is sent to a server or stored. You can paste output that contains account IDs or resource names, and you can use the page offline once it has loaded.
Rates and rules change; check the source before you rely on a figure.
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Same job, other tools: JSONPath Evaluator – Evaluate a JSONPath expression and get the matching values and their paths.
On the related tools: Readability Checker – Flesch reading ease and grade level, with what to change.