diff --git a/projects/natural/src/lib/classes/abstract-detail.ts b/projects/natural/src/lib/classes/abstract-detail.ts
index 492a21a0..90e4fcff 100644
--- a/projects/natural/src/lib/classes/abstract-detail.ts
+++ b/projects/natural/src/lib/classes/abstract-detail.ts
@@ -36,7 +36,10 @@ export class NaturalAbstractDetail<Tone,
 
     public static getFormGroup(model, service) {
         const formConfig = service.getFormConfig(model);
-        return new FormGroup(formConfig, {validators: service.getFormGroupValidators()});
+        return new FormGroup(formConfig, {
+            validators: service.getFormGroupValidators(),
+            asyncValidators: service.getFormGroupAsyncValidators()
+        });
     }
 
     /**
diff --git a/projects/natural/src/lib/classes/validators.ts b/projects/natural/src/lib/classes/validators.ts
new file mode 100644
index 00000000..c04632eb
--- /dev/null
+++ b/projects/natural/src/lib/classes/validators.ts
@@ -0,0 +1,42 @@
+import {AbstractControl, AsyncValidatorFn, ValidationErrors} from '@angular/forms';
+import { NaturalQueryVariablesManager } from './query-variable-manager';
+import { NaturalAbstractModelService } from '../services/abstract-model.service';
+import { map } from 'rxjs/operators';
+import { Observable, of } from 'rxjs';
+
+export class NaturalValidators {
+
+    /**
+     * Returns an async validator function that checks that the form control value is unique
+     */
+    public static unique(
+        fieldName: string,
+        modelService: NaturalAbstractModelService<any, any, any, any, any, any, any, any, any>): AsyncValidatorFn {
+
+        const validator = (control: AbstractControl): Observable<ValidationErrors | null> => {
+
+            const condition = {};
+
+            if (control.value) {
+
+                condition[fieldName] = {equal: {value: control.value}};
+                const variables: any = {
+                    pagination: {pageIndex: 0, pageSize: 0},
+                    filter: {groups: [{conditions: [condition]}]},
+                };
+
+                const qvm = new NaturalQueryVariablesManager<any>();
+                qvm.set('variables', variables);
+
+                return modelService.count(qvm).pipe(
+                    map((count: number) => {
+                        return count > 0 ? {duplicateValue: count} : null;
+                    }),
+                );
+            }
+
+            return of(null);
+        };
+        return validator;
+    }
+}
diff --git a/projects/natural/src/lib/services/abstract-model.service.spec.ts b/projects/natural/src/lib/services/abstract-model.service.spec.ts
index 9a21e773..549775da 100644
--- a/projects/natural/src/lib/services/abstract-model.service.spec.ts
+++ b/projects/natural/src/lib/services/abstract-model.service.spec.ts
@@ -148,6 +148,23 @@ export abstract class AbstractModelServiceSpec {
                 expect(Object.keys(object).length).toBeGreaterThan(keysAfterCreation); // should show created + updated objects merged
             })),
         );
+
+        it('should count existing values',
+            fakeAsync(inject([serviceClass], (service: ModelService) => {
+                const qvm = new NaturalQueryVariablesManager<any>();
+                const variables: any = {
+                    pagination: {pageIndex: 0, pageSize: 0},
+                    filter: {groups: [{conditions: [{slug: 'test string'}]}]},
+                };
+                qvm.set('variables', variables);
+                expect(() => service.count(qvm).subscribe()).toEqual(1);
+
+                variables['filter']['groups'][0]['conditions'][0]['slug'] = 'other string';
+                qvm.set('variables', variables);
+                expect(() => service.count(qvm).subscribe()).toEqual(0);
+
+            })),
+        );
     }
 
     private static expectNotConfiguredOrEqual(expectSuccess: boolean,
diff --git a/projects/natural/src/lib/services/abstract-model.service.ts b/projects/natural/src/lib/services/abstract-model.service.ts
index 8fe3f8c9..a5827e41 100644
--- a/projects/natural/src/lib/services/abstract-model.service.ts
+++ b/projects/natural/src/lib/services/abstract-model.service.ts
@@ -1,4 +1,4 @@
-import { ValidatorFn } from '@angular/forms';
+import gql from 'graphql-tag';
 import { Apollo } from 'apollo-angular';
 import { NetworkStatus } from 'apollo-client';
 import { FetchResult } from 'apollo-link';
@@ -10,11 +10,16 @@ import { NaturalFormControl } from '../classes/form-control';
 import { NaturalQueryVariablesManager } from '../classes/query-variable-manager';
 import { NaturalUtility } from '../classes/utility';
 import { Literal } from '../types/types';
+import {AsyncValidatorFn, ValidatorFn} from '@angular/forms';
 
 export interface FormValidators {
     [key: string]: ValidatorFn[];
 }
 
+export interface FormAsyncValidators {
+    [key: string]: AsyncValidatorFn[];
+}
+
 export interface VariablesWithInput {
     input: Literal;
 }
@@ -67,6 +72,13 @@ export abstract class NaturalAbstractModelService<Tone,
         return {};
     }
 
+    /**
+     * List of individual async fields validators
+     */
+    public getFormAsyncValidators(): FormAsyncValidators {
+        return {};
+    }
+
     /**
      * List of grouped fields validators (like password + confirm password)
      */
@@ -74,9 +86,17 @@ export abstract class NaturalAbstractModelService<Tone,
         return [];
     }
 
+    /**
+     * List of async group fields validators (like unique constraint on multiple columns)
+     */
+    public getFormGroupAsyncValidators(): AsyncValidatorFn[] {
+        return [];
+    }
+
     public getFormConfig(model: Literal): Literal {
         const values = this.getConsolidatedForClient();
         const validators = this.getFormValidators();
+        const asyncValidators = this.getFormAsyncValidators();
         const config = {};
         const disabled = model.permissions ? !model.permissions.update : false;
 
@@ -92,8 +112,9 @@ export abstract class NaturalAbstractModelService<Tone,
                 disabled: disabled,
             };
             const validator = typeof validators[key] !== 'undefined' ? validators[key] : null;
+            const asyncValidator = typeof asyncValidators[key] !== 'undefined' ? asyncValidators[key] : null;
 
-            config[key] = new NaturalFormControl(formState, validator);
+            config[key] = new NaturalFormControl(formState, validator, asyncValidator);
         }
 
         // Configure form for extra validators that are not on a specific field
@@ -108,6 +129,19 @@ export abstract class NaturalAbstractModelService<Tone,
             }
         }
 
+        for (const key of Object.keys(asyncValidators)) {
+            if (config[key] && asyncValidators[key]) {
+                config[key].setAsyncValidators(asyncValidators[key]);
+            } else {
+                const formState = {
+                    value: model[key] ? model[key] : null,
+                    disabled: disabled,
+                };
+
+                config[key] = new NaturalFormControl(formState, null, asyncValidators[key]);
+            }
+        }
+
         return config;
     }
 
@@ -456,6 +490,29 @@ export abstract class NaturalAbstractModelService<Tone,
         return input;
     }
 
+    /**
+     * Return the number of objects matching the query
+     *
+     * This is used for the unique validator
+     *
+     * @TODO: use debounce or Observable.timer to avoid sending a query too often
+     */
+    public count(queryVariablesManager: NaturalQueryVariablesManager<Vall>): Observable<number> {
+        const plural = NaturalUtility.makePlural(this.name);
+        let query = 'query Count' + NaturalUtility.upperCaseFirstLetter(plural);
+        query += '($filter: ' + NaturalUtility.upperCaseFirstLetter(this.name) + 'Filter) {';
+        query += plural + '(filter: $filter, pagination: {pageSize: 0}) { length } }';
+        query = gql(query);
+        return this.apollo.query({
+            query: query,
+            variables: queryVariablesManager.variables.value,
+        }).pipe(
+            map((result) => {
+                return result.data[plural].length as number;
+            }),
+        );
+    }
+
     /**
      * Return empty object with some default values from server perspective
      *
diff --git a/projects/natural/src/lib/testing/mock-apollo.provider.ts b/projects/natural/src/lib/testing/mock-apollo.provider.ts
index fbe6b5d0..dde91738 100644
--- a/projects/natural/src/lib/testing/mock-apollo.provider.ts
+++ b/projects/natural/src/lib/testing/mock-apollo.provider.ts
@@ -33,6 +33,7 @@ const typeDefs = `
 
     type Post {
         id: ID!
+        slug: String
         blog: Blog
     }
 
diff --git a/projects/natural/src/public-api.ts b/projects/natural/src/public-api.ts
index 045f6ff0..6333dbdb 100644
--- a/projects/natural/src/public-api.ts
+++ b/projects/natural/src/public-api.ts
@@ -12,6 +12,7 @@ export * from './lib/classes/data-source';
 export * from './lib/classes/form-control';
 export * from './lib/classes/query-variable-manager';
 export * from './lib/classes/utility';
+export * from './lib/classes/validators';
 
 export * from './lib/services/abstract-model.service';
 export * from './lib/services/enum.service';