diff --git a/tests/test_processors.py b/tests/test_processors.py
index 87c6d263..adec74a2 100644
--- a/tests/test_processors.py
+++ b/tests/test_processors.py
@@ -13,7 +13,9 @@
     brand_processor,
     breadcrumbs_processor,
     gtin_processor,
+    list_processor,
     rating_processor,
+    string_processor,
 )
 
 base_url = "http://www.example.com/blog/"
@@ -321,3 +323,46 @@ def aggregateRating(self):
     assert page.aggregateRating == AggregateRating(
         ratingValue=3.8, bestRating=10, reviewCount=5
     )
+
+
+@pytest.mark.parametrize(
+    "input_value,expected_value",
+    [
+        (None, None),
+        ("", ""),
+        ("Value ", "Value"),
+        (" Value", "Value"),
+        (" Value ", "Value"),
+        ("Multiword value ", "Multiword value"),
+        (" Multiword value", "Multiword value"),
+        (" Multiword value ", "Multiword value"),
+    ],
+)
+def test_string_processor(input_value, expected_value):
+    class RatingPage(BasePage):
+        @field(out=[string_processor])
+        def name(self):
+            return input_value
+
+    page = RatingPage(base_url)  # type: ignore[arg-type]
+    assert page.name == expected_value
+
+
+@pytest.mark.parametrize(
+    "input_value,expected_value",
+    [
+        (None, None),
+        ([], []),
+        (["a", "b"], ["a", "b"]),
+        ([" a", "b "], ["a", "b"]),
+        ([" a ", " b "], ["a", "b"]),
+    ],
+)
+def test_list_processor(input_value, expected_value):
+    class RatingPage(BasePage):
+        @field(out=[list_processor(string_processor)])
+        def name(self):
+            return input_value
+
+    page = RatingPage(base_url)  # type: ignore[arg-type]
+    assert page.name == expected_value
diff --git a/tox.ini b/tox.ini
index 27bf6d3a..50f412cc 100644
--- a/tox.ini
+++ b/tox.ini
@@ -73,7 +73,7 @@ commands = mypy zyte_common_items tests
 [testenv:twinecheck]
 basepython = python3
 deps =
-    twine==4.0.2
+    twine==5.1.1
     build==0.10.0
 commands =
     python -m build --sdist
diff --git a/zyte_common_items/pages/article.py b/zyte_common_items/pages/article.py
index 55add465..bd8d30c8 100644
--- a/zyte_common_items/pages/article.py
+++ b/zyte_common_items/pages/article.py
@@ -6,24 +6,38 @@
 from zyte_common_items.components import Audio, Author, Breadcrumb, Image, Video
 from zyte_common_items.fields import auto_field
 from zyte_common_items.items import Article, ArticleMetadata
-from zyte_common_items.processors import breadcrumbs_processor
+from zyte_common_items.processors import breadcrumbs_processor, string_processor
 
 from .base import BasePage, Page
 from .mixins import HasMetadata
 
 
+class _ArticleProcessors(BasePage.Processors):
+    breadcrumbs = [breadcrumbs_processor]
+    headline = [string_processor]
+    datePublished = [string_processor]
+    datePublishedRaw = [string_processor]
+    dateModified = [string_processor]
+    dateModifiedRaw = [string_processor]
+    inLanguage = [string_processor]
+    description = [string_processor]
+    articleBody = [string_processor]
+    articleBodyHtml = [string_processor]
+    canonicalUrl = [string_processor]
+
+
 class BaseArticlePage(BasePage, Returns[Article], HasMetadata[ArticleMetadata]):
     """:class:`BasePage` subclass for :class:`Article`."""
 
-    class Processors(BasePage.Processors):
-        breadcrumbs = [breadcrumbs_processor]
+    class Processors(_ArticleProcessors):
+        pass
 
 
 class ArticlePage(Page, Returns[Article], HasMetadata[ArticleMetadata]):
     """:class:`Page` subclass for :class:`Article`."""
 
-    class Processors(Page.Processors):
-        breadcrumbs = [breadcrumbs_processor]
+    class Processors(_ArticleProcessors):
+        pass
 
 
 @attrs.define
diff --git a/zyte_common_items/pages/article_list.py b/zyte_common_items/pages/article_list.py
index 40b15c56..d17cfd01 100644
--- a/zyte_common_items/pages/article_list.py
+++ b/zyte_common_items/pages/article_list.py
@@ -6,26 +6,31 @@
 from zyte_common_items.components import Breadcrumb
 from zyte_common_items.fields import auto_field
 from zyte_common_items.items import ArticleFromList, ArticleList, ArticleListMetadata
-from zyte_common_items.processors import breadcrumbs_processor
+from zyte_common_items.processors import breadcrumbs_processor, string_processor
 
 from .base import BasePage, Page
 from .mixins import HasMetadata
 
 
+class _ArticleListProcessors(BasePage.Processors):
+    breadcrumbs = [breadcrumbs_processor]
+    canonicalUrl = [string_processor]
+
+
 class BaseArticleListPage(
     BasePage, Returns[ArticleList], HasMetadata[ArticleListMetadata]
 ):
     """:class:`BasePage` subclass for :class:`ArticleList`."""
 
-    class Processors(BasePage.Processors):
-        breadcrumbs = [breadcrumbs_processor]
+    class Processors(_ArticleListProcessors):
+        pass
 
 
 class ArticleListPage(Page, Returns[ArticleList], HasMetadata[ArticleListMetadata]):
     """:class:`Page` subclass for :class:`ArticleList`."""
 
-    class Processors(Page.Processors):
-        breadcrumbs = [breadcrumbs_processor]
+    class Processors(_ArticleListProcessors):
+        pass
 
 
 @attrs.define
diff --git a/zyte_common_items/pages/article_navigation.py b/zyte_common_items/pages/article_navigation.py
index 7a84d39d..c51e3267 100644
--- a/zyte_common_items/pages/article_navigation.py
+++ b/zyte_common_items/pages/article_navigation.py
@@ -6,22 +6,33 @@
 from zyte_common_items.components import ProbabilityRequest, Request
 from zyte_common_items.fields import auto_field
 from zyte_common_items.items import ArticleNavigation, ArticleNavigationMetadata
+from zyte_common_items.processors import string_processor
 
 from .base import BasePage, Page
 from .mixins import HasMetadata
 
 
+class _ArticleNavigationProcessors(BasePage.Processors):
+    categoryName = [string_processor]
+
+
 class BaseArticleNavigationPage(
     BasePage, Returns[ArticleNavigation], HasMetadata[ArticleNavigationMetadata]
 ):
     """:class:`BasePage` subclass for :class:`ArticleNavigation`."""
 
+    class Processors(_ArticleNavigationProcessors):
+        pass
+
 
 class ArticleNavigationPage(
     Page, Returns[ArticleNavigation], HasMetadata[ArticleNavigationMetadata]
 ):
     """:class:`Page` subclass for :class:`ArticleNavigation`."""
 
+    class Processors(_ArticleNavigationProcessors):
+        pass
+
 
 @attrs.define
 class AutoArticleNavigationPage(BaseArticleNavigationPage):
diff --git a/zyte_common_items/pages/base.py b/zyte_common_items/pages/base.py
index fc36e5d2..45c1a7f9 100644
--- a/zyte_common_items/pages/base.py
+++ b/zyte_common_items/pages/base.py
@@ -3,7 +3,7 @@
 from web_poet.pages import ItemT
 
 from .._dateutils import utcnow_formatted
-from ..processors import metadata_processor
+from ..processors import metadata_processor, string_processor
 from .mixins import HasMetadata, MetadataT
 
 
@@ -43,12 +43,16 @@ def no_item_found(self) -> ItemT:
         )
 
 
+class _BaseProcessors(_BasePage.Processors):
+    url = [string_processor]
+
+
 @attrs.define
 class BasePage(_BasePage):
     """Base class for page object classes that has
     :class:`~web_poet.page_inputs.http.RequestUrl` as a dependency."""
 
-    class Processors(_BasePage.Processors):
+    class Processors(_BaseProcessors):
         pass
 
     request_url: RequestUrl
@@ -63,7 +67,7 @@ class Page(_BasePage, WebPage):
     """Base class for page object classes that has
     :class:`~web_poet.page_inputs.http.HttpResponse` as a dependency."""
 
-    class Processors(_BasePage.Processors):
+    class Processors(_BaseProcessors):
         pass
 
     @field
diff --git a/zyte_common_items/pages/business_place.py b/zyte_common_items/pages/business_place.py
index c0ec6ab6..cee11e6d 100644
--- a/zyte_common_items/pages/business_place.py
+++ b/zyte_common_items/pages/business_place.py
@@ -16,20 +16,39 @@
 )
 from zyte_common_items.fields import auto_field
 from zyte_common_items.items import BusinessPlace, BusinessPlaceMetadata
-from zyte_common_items.processors import description_processor, rating_processor
+from zyte_common_items.processors import (
+    description_processor,
+    list_processor,
+    rating_processor,
+    string_processor,
+)
 
 from .base import BasePage, Page
 from .mixins import HasMetadata
 
 
+class _BusinessPlaceProcessors(BasePage.Processors):
+    aggregateRating = [rating_processor]
+    description = [description_processor]
+    categories = [list_processor(string_processor)]
+    features = [list_processor(string_processor)]
+    map = [string_processor]
+    name = [string_processor]
+    placeId = [string_processor]
+    priceRange = [string_processor]
+    tags = [list_processor(string_processor)]
+    telephone = [string_processor]
+    timezone = [string_processor]
+    website = [string_processor]
+
+
 class BaseBusinessPlacePage(
     BasePage, Returns[BusinessPlace], HasMetadata[BusinessPlaceMetadata]
 ):
     """:class:`BasePage` subclass for :class:`BusinessPlace`."""
 
-    class Processors(BasePage.Processors):
-        aggregateRating = [rating_processor]
-        description = [description_processor]
+    class Processors(_BusinessPlaceProcessors):
+        pass
 
 
 class BusinessPlacePage(
@@ -37,9 +56,8 @@ class BusinessPlacePage(
 ):
     """:class:`Page` subclass for :class:`BusinessPlace`."""
 
-    class Processors(Page.Processors):
-        aggregateRating = [rating_processor]
-        description = [description_processor]
+    class Processors(_BusinessPlaceProcessors):
+        pass
 
 
 @attrs.define
diff --git a/zyte_common_items/pages/job_posting.py b/zyte_common_items/pages/job_posting.py
index a48a95be..119136e0 100644
--- a/zyte_common_items/pages/job_posting.py
+++ b/zyte_common_items/pages/job_posting.py
@@ -9,20 +9,40 @@
 from zyte_common_items.processors import (
     description_html_processor,
     description_processor,
+    list_processor,
+    string_processor,
 )
 
 from .base import BasePage, Page
 from .mixins import DescriptionMixin, HasMetadata
 
 
+class _JobPostingProcessors(BasePage.Processors):
+    description = [description_processor]
+    descriptionHtml = [description_html_processor]
+    jobPostingId = [string_processor]
+    datePublished = [string_processor]
+    datePublishedRaw = [string_processor]
+    dateModified = [string_processor]
+    dateModifiedRaw = [string_processor]
+    validThrough = [string_processor]
+    validThroughRaw = [string_processor]
+    jobTitle = [string_processor]
+    headline = [string_processor]
+    employmentType = [string_processor]
+    requirements = [list_processor(string_processor)]
+    jobStartDate = [string_processor]
+    jobStartDateRaw = [string_processor]
+    remoteStatus = [string_processor]
+
+
 class BaseJobPostingPage(
     BasePage, DescriptionMixin, Returns[JobPosting], HasMetadata[JobPostingMetadata]
 ):
     """:class:`BasePage` subclass for :class:`JobPosting`."""
 
-    class Processors(BasePage.Processors):
-        description = [description_processor]
-        descriptionHtml = [description_html_processor]
+    class Processors(_JobPostingProcessors):
+        pass
 
 
 class JobPostingPage(
@@ -30,9 +50,8 @@ class JobPostingPage(
 ):
     """:class:`Page` subclass for :class:`JobPosting`."""
 
-    class Processors(Page.Processors):
-        description = [description_processor]
-        descriptionHtml = [description_html_processor]
+    class Processors(_JobPostingProcessors):
+        pass
 
 
 @attrs.define
diff --git a/zyte_common_items/pages/product.py b/zyte_common_items/pages/product.py
index fc297629..1973d46d 100644
--- a/zyte_common_items/pages/product.py
+++ b/zyte_common_items/pages/product.py
@@ -19,15 +19,40 @@
     description_html_processor,
     description_processor,
     gtin_processor,
+    list_processor,
     price_processor,
     rating_processor,
     simple_price_processor,
+    string_processor,
 )
 
 from .base import BasePage, Page
 from .mixins import DescriptionMixin, HasMetadata, PriceMixin
 
 
+class _ProductProcessors(BasePage.Processors):
+    aggregateRating = [rating_processor]
+    brand = [brand_processor]
+    breadcrumbs = [breadcrumbs_processor]
+    description = [description_processor]
+    descriptionHtml = [description_html_processor]
+    gtin = [gtin_processor]
+    price = [price_processor]
+    regularPrice = [simple_price_processor]
+    availability = [string_processor]
+    canonicalUrl = [string_processor]
+    color = [string_processor]
+    currency = [string_processor]
+    currencyRaw = [string_processor]
+    features = [list_processor(string_processor)]
+    mpn = [string_processor]
+    name = [string_processor]
+    productId = [string_processor]
+    size = [string_processor]
+    sku = [string_processor]
+    style = [string_processor]
+
+
 class BaseProductPage(
     BasePage,
     DescriptionMixin,
@@ -37,15 +62,8 @@ class BaseProductPage(
 ):
     """:class:`BasePage` subclass for :class:`Product`."""
 
-    class Processors(BasePage.Processors):
-        aggregateRating = [rating_processor]
-        brand = [brand_processor]
-        breadcrumbs = [breadcrumbs_processor]
-        description = [description_processor]
-        descriptionHtml = [description_html_processor]
-        gtin = [gtin_processor]
-        price = [price_processor]
-        regularPrice = [simple_price_processor]
+    class Processors(_ProductProcessors):
+        pass
 
 
 class ProductPage(
@@ -53,15 +71,8 @@ class ProductPage(
 ):
     """:class:`Page` subclass for :class:`Product`."""
 
-    class Processors(Page.Processors):
-        aggregateRating = [rating_processor]
-        brand = [brand_processor]
-        breadcrumbs = [breadcrumbs_processor]
-        description = [description_processor]
-        descriptionHtml = [description_html_processor]
-        gtin = [gtin_processor]
-        price = [price_processor]
-        regularPrice = [simple_price_processor]
+    class Processors(_ProductProcessors):
+        pass
 
 
 @attrs.define
diff --git a/zyte_common_items/pages/product_list.py b/zyte_common_items/pages/product_list.py
index e115b4c4..d2553f3a 100644
--- a/zyte_common_items/pages/product_list.py
+++ b/zyte_common_items/pages/product_list.py
@@ -6,26 +6,32 @@
 from zyte_common_items.components import Breadcrumb, Link
 from zyte_common_items.fields import auto_field
 from zyte_common_items.items import ProductFromList, ProductList, ProductListMetadata
-from zyte_common_items.processors import breadcrumbs_processor
+from zyte_common_items.processors import breadcrumbs_processor, string_processor
 
 from .base import BasePage, Page
 from .mixins import HasMetadata
 
 
+class _ProductListProcessors(BasePage.Processors):
+    breadcrumbs = [breadcrumbs_processor]
+    canonicalUrl = [string_processor]
+    categoryName = [string_processor]
+
+
 class BaseProductListPage(
     BasePage, Returns[ProductList], HasMetadata[ProductListMetadata]
 ):
     """:class:`BasePage` subclass for :class:`ProductList`."""
 
-    class Processors(BasePage.Processors):
-        breadcrumbs = [breadcrumbs_processor]
+    class Processors(_ProductListProcessors):
+        pass
 
 
 class ProductListPage(Page, Returns[ProductList], HasMetadata[ProductListMetadata]):
     """:class:`Page` subclass for :class:`ProductList`."""
 
-    class Processors(Page.Processors):
-        breadcrumbs = [breadcrumbs_processor]
+    class Processors(_ProductListProcessors):
+        pass
 
 
 @attrs.define
diff --git a/zyte_common_items/pages/product_navigation.py b/zyte_common_items/pages/product_navigation.py
index 7ed00d9b..cd6bee6a 100644
--- a/zyte_common_items/pages/product_navigation.py
+++ b/zyte_common_items/pages/product_navigation.py
@@ -6,20 +6,28 @@
 from zyte_common_items.components import ProbabilityRequest, Request
 from zyte_common_items.fields import auto_field
 from zyte_common_items.items import ProductNavigation, ProductNavigationMetadata
-from zyte_common_items.processors import probability_request_list_processor
+from zyte_common_items.processors import (
+    probability_request_list_processor,
+    string_processor,
+)
 
 from .base import BasePage, Page
 from .mixins import HasMetadata
 
 
+class _ProductNavigationProcessors(BasePage.Processors):
+    subCategories = [probability_request_list_processor]
+    items = [probability_request_list_processor]
+    categoryName = [string_processor]
+
+
 class BaseProductNavigationPage(
     BasePage, Returns[ProductNavigation], HasMetadata[ProductNavigationMetadata]
 ):
     """:class:`BasePage` subclass for :class:`ProductNavigation`."""
 
-    class Processors(BasePage.Processors):
-        subCategories = [probability_request_list_processor]
-        items = [probability_request_list_processor]
+    class Processors(_ProductNavigationProcessors):
+        pass
 
 
 class ProductNavigationPage(
@@ -27,6 +35,9 @@ class ProductNavigationPage(
 ):
     """:class:`Page` subclass for :class:`ProductNavigation`."""
 
+    class Processors(_ProductNavigationProcessors):
+        pass
+
 
 @attrs.define
 class AutoProductNavigationPage(BaseProductNavigationPage):
diff --git a/zyte_common_items/pages/real_estate.py b/zyte_common_items/pages/real_estate.py
index e869e703..71f809c6 100644
--- a/zyte_common_items/pages/real_estate.py
+++ b/zyte_common_items/pages/real_estate.py
@@ -13,27 +13,41 @@
 from zyte_common_items.fields import auto_field
 from zyte_common_items.items import RealEstate, RealEstateMetadata
 
-from ..processors import breadcrumbs_processor, description_processor
+from ..processors import breadcrumbs_processor, description_processor, string_processor
 from .base import BasePage, Page
 from .mixins import HasMetadata
 
 
+class _RealEstateProcessors(BasePage.Processors):
+    breadcrumbs = [breadcrumbs_processor]
+    description = [description_processor]
+    currency = [string_processor]
+    currencyRaw = [string_processor]
+    datePublished = [string_processor]
+    datePublishedRaw = [string_processor]
+    name = [string_processor]
+    price = [string_processor]
+    propertyType = [string_processor]
+    realEstateId = [string_processor]
+    rentalPeriod = [string_processor]
+    tradeType = [string_processor]
+    virtualTourUrl = [string_processor]
+
+
 class BaseRealEstatePage(
     BasePage, Returns[RealEstate], HasMetadata[RealEstateMetadata]
 ):
     """:class:`BasePage` subclass for :class:`RealEstate`."""
 
-    class Processors(BasePage.Processors):
-        breadcrumbs = [breadcrumbs_processor]
-        description = [description_processor]
+    class Processors(_RealEstateProcessors):
+        pass
 
 
 class RealEstatePage(Page, Returns[RealEstate], HasMetadata[RealEstateMetadata]):
     """:class:`Page` subclass for :class:`RealEstate`."""
 
-    class Processors(Page.Processors):
-        breadcrumbs = [breadcrumbs_processor]
-        description = [description_processor]
+    class Processors(_RealEstateProcessors):
+        pass
 
 
 @attrs.define
diff --git a/zyte_common_items/pages/social_media_post.py b/zyte_common_items/pages/social_media_post.py
index a4f7823c..0dee9319 100644
--- a/zyte_common_items/pages/social_media_post.py
+++ b/zyte_common_items/pages/social_media_post.py
@@ -6,21 +6,31 @@
 from zyte_common_items.components import Reactions, SocialMediaPostAuthor, Url
 from zyte_common_items.fields import auto_field
 from zyte_common_items.items import SocialMediaPost, SocialMediaPostMetadata
+from zyte_common_items.processors import list_processor, string_processor
 
 from .base import BasePage, Page
 from .mixins import HasMetadata
 
 
+class _SocialMediaPostProcessors(BasePage.Processors):
+    postId = [string_processor]
+    text = [string_processor]
+    datePublished = [string_processor]
+    hashtags = [list_processor(string_processor)]
+
+
 class BaseSocialMediaPostPage(
     BasePage, Returns[SocialMediaPost], HasMetadata[SocialMediaPostMetadata]
 ):
-    pass
+    class Processors(_SocialMediaPostProcessors):
+        pass
 
 
 class SocialMediaPostPage(
     Page, Returns[SocialMediaPost], HasMetadata[SocialMediaPostMetadata]
 ):
-    pass
+    class Processors(_SocialMediaPostProcessors):
+        pass
 
 
 @attrs.define
diff --git a/zyte_common_items/processors.py b/zyte_common_items/processors.py
index e4306c11..4fc86bd0 100644
--- a/zyte_common_items/processors.py
+++ b/zyte_common_items/processors.py
@@ -345,3 +345,21 @@ def metadata_processor(metadata: BaseMetadata, page):
     if page.metadata_cls is None:
         return None
     return metadata.cast(page.metadata_cls)
+
+
+def string_processor(value: str) -> Union[str, None]:
+    """Processor for string values"""
+    if isinstance(value, str):
+        return value.strip()
+    return value
+
+
+def list_processor(processor: Callable) -> Any:
+    """Apply processor to a list of items"""
+
+    def loop(values):
+        if not isinstance(values, Iterable):
+            return values
+        return [processor(value) for value in values]
+
+    return loop