diff --git a/changelog.d/20251218_163750_rosswilsonblair_use_default_config_file.md b/changelog.d/20251218_163750_rosswilsonblair_use_default_config_file.md
new file mode 100644
index 000000000..adf056b11
--- /dev/null
+++ b/changelog.d/20251218_163750_rosswilsonblair_use_default_config_file.md
@@ -0,0 +1,47 @@
+<!--
+A new scriv changelog fragment.
+
+Uncomment the section that is right (remove the HTML comment wrapper).
+For top level release notes, leave all the headers commented out.
+-->
+
+<!--
+### Added
+
+- A bullet item for the Added category.
+
+-->
+<!--
+### Changed
+
+- A bullet item for the Changed category.
+
+-->
+### Fixed
+
+- CLI and web validator now default to loading '.bids-validator-config.json'. Validator only attempts this if no other config file was passed in.
+
+<!--
+### Deprecated
+
+- A bullet item for the Deprecated category.
+
+-->
+<!--
+### Removed
+
+- A bullet item for the Removed category.
+
+-->
+<!--
+### Security
+
+- A bullet item for the Security category.
+
+-->
+<!--
+### Infrastructure
+
+- A bullet item for the Infrastructure category.
+
+-->
diff --git a/src/main.ts b/src/main.ts
index fdcf0f42d..bb31b4059 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -4,7 +4,8 @@ import * as colors from '@std/fmt/colors'
 import { readFileTree } from './files/deno.ts'
 import { fileListToTree } from './files/browser.ts'
 import { FileIgnoreRules } from './files/ignore.ts'
-import { resolve } from '@std/path'
+import { join, resolve } from '@std/path'
+import { exists } from "jsr:@std/fs/exists";
 import { validate } from './validators/bids.ts'
 import { consoleFormat, resultToJSONStr } from './utils/output.ts'
 import { setupLogging } from './utils/logger.ts'
@@ -28,7 +29,21 @@ export async function main(): Promise<ValidationResult> {
     : undefined
   const tree = await readFileTree(absolutePath, prune, options.preferredRemote)
 
-  const config = options.config ? JSON.parse(Deno.readTextFileSync(options.config)) as Config : {}
+  let config = {}
+  if (options.config) {
+    config = JSON.parse(Deno.readTextFileSync(options.config))
+  } else {
+       const defaultConfig = join(absolutePath, '.bids-validator-config.json') 
+    try {
+      await Deno.lstat(defaultConfig)
+       config = JSON.parse(Deno.readTextFileSync(defaultConfig))
+       options.config = defaultConfig
+    } catch {
+      if (!(err instanceof Deno.errors.NotFound)) {
+        throw err;
+      }
+    }
+  }
 
   // Run the schema based validator
   const schemaResult = await validate(tree, options, config)
diff --git a/web/src/App.tsx b/web/src/App.tsx
index 4cf2e733c..8c54a1f26 100644
--- a/web/src/App.tsx
+++ b/web/src/App.tsx
@@ -1,6 +1,6 @@
 import React, { useState } from "react"
 import "./App.css"
-import { directoryOpen } from "https://esm.sh/browser-fs-access@0.35.0"
+import { directoryOpen, fileOpen } from "https://esm.sh/browser-fs-access@0.35.0"
 import confetti from 'https://cdn.jsdelivr.net/npm/canvas-confetti@1.9.3/dist/confetti.module.mjs';
 import { fileListToTree, validate, getVersion } from "../dist/validator/main.js"
 import type { ValidationResult } from "../../src/types/validation-result.ts"
@@ -50,11 +50,19 @@ function App() {
   const [validation, setValidation] = useState<ValidationResult>()
 
   async function validateDir() {
+    
     const dirHandle = await directoryOpen({
       recursive: true,
     })
+    let config = {}
+    const configFile = dirHandle.find(file => file.name ==='.bids-validator-config.json') 
+    if (configFile) {
+      config = configFile.text().then(text => JSON.parse(text)).catch((err) => {
+        alert(`Failed to load ".bids-validator-config.json". \n\nUsing empty configuration object:\n\n${err}`)
+      })
+    }
     const fileTree = await fileListToTree(dirHandle)
-    setValidation(await validate(fileTree, {}))
+    setValidation(await validate(fileTree, config))
   }
 
   const [version, setVersion] = useState<string>()